diff --git a/lib/importlib_metadata/__init__.py b/lib/importlib_metadata/__init__.py
index 2c71d33c..46a14e64 100644
--- a/lib/importlib_metadata/__init__.py
+++ b/lib/importlib_metadata/__init__.py
@@ -1,24 +1,34 @@
+"""
+APIs exposing metadata from third-party Python packages.
+
+This codebase is shared between importlib.metadata in the stdlib
+and importlib_metadata in PyPI. See
+https://github.com/python/importlib_metadata/wiki/Development-Methodology
+for more detail.
+"""
+
 from __future__ import annotations
 
-import os
-import re
 import abc
-import sys
-import json
-import zipp
+import collections
 import email
-import types
-import inspect
-import pathlib
-import operator
-import textwrap
 import functools
 import itertools
+import operator
+import os
+import pathlib
 import posixpath
-import collections
+import re
+import sys
+import textwrap
+import types
+from contextlib import suppress
+from importlib import import_module
+from importlib.abc import MetaPathFinder
+from itertools import starmap
+from typing import Any, Iterable, List, Mapping, Match, Optional, Set, cast
 
 from . import _meta
-from .compat import py39, py311
 from ._collections import FreezableDefaultDict, Pair
 from ._compat import (
     NullFinder,
@@ -27,12 +37,7 @@ from ._compat import (
 from ._functools import method_cache, pass_none
 from ._itertools import always_iterable, bucket, unique_everseen
 from ._meta import PackageMetadata, SimplePath
-
-from contextlib import suppress
-from importlib import import_module
-from importlib.abc import MetaPathFinder
-from itertools import starmap
-from typing import Any, Iterable, List, Mapping, Match, Optional, Set, cast
+from .compat import py39, py311
 
 __all__ = [
     'Distribution',
@@ -58,7 +63,7 @@ class PackageNotFoundError(ModuleNotFoundError):
         return f"No package metadata was found for {self.name}"
 
     @property
-    def name(self) -> str:  # type: ignore[override]
+    def name(self) -> str:  # type: ignore[override] # make readonly
         (name,) = self.args
         return name
 
@@ -227,9 +232,26 @@ class EntryPoint:
         >>> ep.matches(attr='bong')
         True
         """
+        self._disallow_dist(params)
         attrs = (getattr(self, param) for param in params)
         return all(map(operator.eq, params.values(), attrs))
 
+    @staticmethod
+    def _disallow_dist(params):
+        """
+        Querying by dist is not allowed (dist objects are not comparable).
+        >>> EntryPoint(name='fan', value='fav', group='fag').matches(dist='foo')
+        Traceback (most recent call last):
+        ...
+        ValueError: "dist" is not suitable for matching...
+        """
+        if "dist" in params:
+            raise ValueError(
+                '"dist" is not suitable for matching. '
+                "Instead, use Distribution.entry_points.select() on a "
+                "located distribution."
+            )
+
     def _key(self):
         return self.name, self.value, self.group
 
@@ -259,7 +281,7 @@ class EntryPoints(tuple):
 
     __slots__ = ()
 
-    def __getitem__(self, name: str) -> EntryPoint:  # type: ignore[override]
+    def __getitem__(self, name: str) -> EntryPoint:  # type: ignore[override] # Work with str instead of int
         """
         Get the EntryPoint in self matching name.
         """
@@ -315,7 +337,7 @@ class PackagePath(pathlib.PurePosixPath):
     size: int
     dist: Distribution
 
-    def read_text(self, encoding: str = 'utf-8') -> str:  # type: ignore[override]
+    def read_text(self, encoding: str = 'utf-8') -> str:
         return self.locate().read_text(encoding=encoding)
 
     def read_binary(self) -> bytes:
@@ -373,6 +395,17 @@ class Distribution(metaclass=abc.ABCMeta):
         """
         Given a path to a file in this distribution, return a SimplePath
         to it.
+
+        This method is used by callers of ``Distribution.files()`` to
+        locate files within the distribution. If it's possible for a
+        Distribution to represent files in the distribution as
+        ``SimplePath`` objects, it should implement this method
+        to resolve such objects.
+
+        Some Distribution providers may elect not to resolve SimplePath
+        objects within the distribution by raising a
+        NotImplementedError, but consumers of such a Distribution would
+        be unable to invoke ``Distribution.files()``.
         """
 
     @classmethod
@@ -639,6 +672,9 @@ class Distribution(metaclass=abc.ABCMeta):
         return self._load_json('direct_url.json')
 
     def _load_json(self, filename):
+        # Deferred for performance (python/importlib_metadata#503)
+        import json
+
         return pass_none(json.loads)(
             self.read_text(filename),
             object_hook=lambda data: types.SimpleNamespace(**data),
@@ -723,7 +759,7 @@ class FastPath:
     True
     """
 
-    @functools.lru_cache()  # type: ignore
+    @functools.lru_cache()  # type: ignore[misc]
     def __new__(cls, root):
         return super().__new__(cls)
 
@@ -741,7 +777,10 @@ class FastPath:
         return []
 
     def zip_children(self):
-        zip_path = zipp.Path(self.root)
+        # deferred for performance (python/importlib_metadata#502)
+        from zipp.compat.overlay import zipfile
+
+        zip_path = zipfile.Path(self.root)
         names = zip_path.root.namelist()
         self.joinpath = zip_path.joinpath
 
@@ -1078,11 +1117,10 @@ def _get_toplevel_name(name: PackagePath) -> str:
     >>> _get_toplevel_name(PackagePath('foo.dist-info'))
     'foo.dist-info'
     """
-    return _topmost(name) or (
-        # python/typeshed#10328
-        inspect.getmodulename(name)  # type: ignore
-        or str(name)
-    )
+    # Defer import of inspect for performance (python/cpython#118761)
+    import inspect
+
+    return _topmost(name) or inspect.getmodulename(name) or str(name)
 
 
 def _top_level_inferred(dist):
diff --git a/lib/importlib_metadata/_adapters.py b/lib/importlib_metadata/_adapters.py
index 6223263e..3b516a2d 100644
--- a/lib/importlib_metadata/_adapters.py
+++ b/lib/importlib_metadata/_adapters.py
@@ -1,6 +1,6 @@
+import email.message
 import re
 import textwrap
-import email.message
 
 from ._text import FoldedCase
 
diff --git a/lib/importlib_metadata/_compat.py b/lib/importlib_metadata/_compat.py
index df312b1c..01356d69 100644
--- a/lib/importlib_metadata/_compat.py
+++ b/lib/importlib_metadata/_compat.py
@@ -1,6 +1,5 @@
-import sys
 import platform
-
+import sys
 
 __all__ = ['install', 'NullFinder']
 
diff --git a/lib/importlib_metadata/_functools.py b/lib/importlib_metadata/_functools.py
index 71f66bd0..5dda6a21 100644
--- a/lib/importlib_metadata/_functools.py
+++ b/lib/importlib_metadata/_functools.py
@@ -1,5 +1,5 @@
-import types
 import functools
+import types
 
 
 # from jaraco.functools 3.3
diff --git a/lib/importlib_metadata/_meta.py b/lib/importlib_metadata/_meta.py
index 1927d0f6..0942bbd9 100644
--- a/lib/importlib_metadata/_meta.py
+++ b/lib/importlib_metadata/_meta.py
@@ -1,9 +1,17 @@
 from __future__ import annotations
 
 import os
-from typing import Protocol
-from typing import Any, Dict, Iterator, List, Optional, TypeVar, Union, overload
-
+from typing import (
+    Any,
+    Dict,
+    Iterator,
+    List,
+    Optional,
+    Protocol,
+    TypeVar,
+    Union,
+    overload,
+)
 
 _T = TypeVar("_T")
 
diff --git a/lib/zipp/__init__.py b/lib/zipp/__init__.py
index d65297b8..031d9d4f 100644
--- a/lib/zipp/__init__.py
+++ b/lib/zipp/__init__.py
@@ -1,16 +1,27 @@
+"""
+A Path-like interface for zipfiles.
+
+This codebase is shared between zipfile.Path in the stdlib
+and zipp in PyPI. See
+https://github.com/python/importlib_metadata/wiki/Development-Methodology
+for more detail.
+"""
+
+import functools
 import io
-import posixpath
-import zipfile
 import itertools
-import contextlib
 import pathlib
+import posixpath
 import re
 import stat
 import sys
+import zipfile
 
 from .compat.py310 import text_encoding
 from .glob import Translator
 
+from ._functools import save_method_args
+
 
 __all__ = ['Path']
 
@@ -37,7 +48,7 @@ def _parents(path):
 def _ancestry(path):
     """
     Given a path with elements separated by
-    posixpath.sep, generate all elements of that path
+    posixpath.sep, generate all elements of that path.
 
     >>> list(_ancestry('b/d'))
     ['b/d', 'b']
@@ -49,9 +60,14 @@ def _ancestry(path):
     ['b']
     >>> list(_ancestry(''))
     []
+
+    Multiple separators are treated like a single.
+
+    >>> list(_ancestry('//b//d///f//'))
+    ['//b//d///f', '//b//d', '//b']
     """
     path = path.rstrip(posixpath.sep)
-    while path and path != posixpath.sep:
+    while path.rstrip(posixpath.sep):
         yield path
         path, tail = posixpath.split(path)
 
@@ -73,82 +89,19 @@ class InitializedState:
     Mix-in to save the initialization state for pickling.
     """
 
+    @save_method_args
     def __init__(self, *args, **kwargs):
-        self.__args = args
-        self.__kwargs = kwargs
         super().__init__(*args, **kwargs)
 
     def __getstate__(self):
-        return self.__args, self.__kwargs
+        return self._saved___init__.args, self._saved___init__.kwargs
 
     def __setstate__(self, state):
         args, kwargs = state
         super().__init__(*args, **kwargs)
 
 
-class SanitizedNames:
-    """
-    ZipFile mix-in to ensure names are sanitized.
-    """
-
-    def namelist(self):
-        return list(map(self._sanitize, super().namelist()))
-
-    @staticmethod
-    def _sanitize(name):
-        r"""
-        Ensure a relative path with posix separators and no dot names.
-
-        Modeled after
-        https://github.com/python/cpython/blob/bcc1be39cb1d04ad9fc0bd1b9193d3972835a57c/Lib/zipfile/__init__.py#L1799-L1813
-        but provides consistent cross-platform behavior.
-
-        >>> san = SanitizedNames._sanitize
-        >>> san('/foo/bar')
-        'foo/bar'
-        >>> san('//foo.txt')
-        'foo.txt'
-        >>> san('foo/.././bar.txt')
-        'foo/bar.txt'
-        >>> san('foo../.bar.txt')
-        'foo../.bar.txt'
-        >>> san('\\foo\\bar.txt')
-        'foo/bar.txt'
-        >>> san('D:\\foo.txt')
-        'D/foo.txt'
-        >>> san('\\\\server\\share\\file.txt')
-        'server/share/file.txt'
-        >>> san('\\\\?\\GLOBALROOT\\Volume3')
-        '?/GLOBALROOT/Volume3'
-        >>> san('\\\\.\\PhysicalDrive1\\root')
-        'PhysicalDrive1/root'
-
-        Retain any trailing slash.
-        >>> san('abc/')
-        'abc/'
-
-        Raises a ValueError if the result is empty.
-        >>> san('../..')
-        Traceback (most recent call last):
-        ...
-        ValueError: Empty filename
-        """
-
-        def allowed(part):
-            return part and part not in {'..', '.'}
-
-        # Remove the drive letter.
-        # Don't use ntpath.splitdrive, because that also strips UNC paths
-        bare = re.sub('^([A-Z]):', r'\1', name, flags=re.IGNORECASE)
-        clean = bare.replace('\\', '/')
-        parts = clean.split('/')
-        joined = '/'.join(filter(allowed, parts))
-        if not joined:
-            raise ValueError("Empty filename")
-        return joined + '/' * name.endswith('/')
-
-
-class CompleteDirs(InitializedState, SanitizedNames, zipfile.ZipFile):
+class CompleteDirs(InitializedState, zipfile.ZipFile):
     """
     A ZipFile subclass that ensures that implied directories
     are always included in the namelist.
@@ -230,16 +183,18 @@ class FastLookup(CompleteDirs):
     """
 
     def namelist(self):
-        with contextlib.suppress(AttributeError):
-            return self.__names
-        self.__names = super().namelist()
-        return self.__names
+        return self._namelist
+
+    @functools.cached_property
+    def _namelist(self):
+        return super().namelist()
 
     def _name_set(self):
-        with contextlib.suppress(AttributeError):
-            return self.__lookup
-        self.__lookup = super()._name_set()
-        return self.__lookup
+        return self._name_set_prop
+
+    @functools.cached_property
+    def _name_set_prop(self):
+        return super()._name_set()
 
 
 def _extract_text_encoding(encoding=None, *args, **kwargs):
@@ -329,7 +284,7 @@ class Path:
     >>> str(path.parent)
     'mem'
 
-    If the zipfile has no filename, such attributes are not
+    If the zipfile has no filename, such attributes are not
     valid and accessing them will raise an Exception.
 
     >>> zf.filename = None
@@ -388,7 +343,7 @@ class Path:
         if self.is_dir():
             raise IsADirectoryError(self)
         zip_mode = mode[0]
-        if not self.exists() and zip_mode == 'r':
+        if zip_mode == 'r' and not self.exists():
             raise FileNotFoundError(self)
         stream = self.root.open(self.at, zip_mode, pwd=pwd)
         if 'b' in mode:
@@ -470,8 +425,7 @@ class Path:
         prefix = re.escape(self.at)
         tr = Translator(seps='/')
         matches = re.compile(prefix + tr.translate(pattern)).fullmatch
-        names = (data.filename for data in self.root.filelist)
-        return map(self._next, filter(matches, names))
+        return map(self._next, filter(matches, self.root.namelist()))
 
     def rglob(self, pattern):
         return self.glob(f'**/{pattern}')
diff --git a/lib/zipp/_functools.py b/lib/zipp/_functools.py
new file mode 100644
index 00000000..f75ae2b0
--- /dev/null
+++ b/lib/zipp/_functools.py
@@ -0,0 +1,20 @@
+import collections
+import functools
+
+
+# from jaraco.functools 4.0.2
+def save_method_args(method):
+    """
+    Wrap a method such that when it is called, the args and kwargs are
+    saved on the method.
+    """
+    args_and_kwargs = collections.namedtuple('args_and_kwargs', 'args kwargs')
+
+    @functools.wraps(method)
+    def wrapper(self, /, *args, **kwargs):
+        attr_name = '_saved_' + method.__name__
+        attr = args_and_kwargs(args, kwargs)
+        setattr(self, attr_name, attr)
+        return method(self, *args, **kwargs)
+
+    return wrapper
diff --git a/lib/zipp/compat/overlay.py b/lib/zipp/compat/overlay.py
new file mode 100644
index 00000000..5a97ee7c
--- /dev/null
+++ b/lib/zipp/compat/overlay.py
@@ -0,0 +1,37 @@
+"""
+Expose zipp.Path as .zipfile.Path.
+
+Includes everything else in ``zipfile`` to match future usage. Just
+use:
+
+>>> from zipp.compat.overlay import zipfile
+
+in place of ``import zipfile``.
+
+Relative imports are supported too.
+
+>>> from zipp.compat.overlay.zipfile import ZipInfo
+
+The ``zipfile`` object added to ``sys.modules`` needs to be
+hashable (#126).
+
+>>> _ = hash(sys.modules['zipp.compat.overlay.zipfile'])
+"""
+
+import importlib
+import sys
+import types
+
+import zipp
+
+
+class HashableNamespace(types.SimpleNamespace):
+    def __hash__(self):
+        return hash(tuple(vars(self)))
+
+
+zipfile = HashableNamespace(**vars(importlib.import_module('zipfile')))
+zipfile.Path = zipp.Path
+zipfile._path = zipp
+
+sys.modules[__name__ + '.zipfile'] = zipfile  # type: ignore[assignment]
diff --git a/lib/zipp/compat/py310.py b/lib/zipp/compat/py310.py
index d5ca53e0..e1e7ec22 100644
--- a/lib/zipp/compat/py310.py
+++ b/lib/zipp/compat/py310.py
@@ -1,5 +1,5 @@
-import sys
 import io
+import sys
 
 
 def _text_encoding(encoding, stacklevel=2, /):  # pragma: no cover
@@ -7,5 +7,7 @@ def _text_encoding(encoding, stacklevel=2, /):  # pragma: no cover
 
 
 text_encoding = (
-    io.text_encoding if sys.version_info > (3, 10) else _text_encoding  # type: ignore
+    io.text_encoding  # type: ignore[unused-ignore, attr-defined]
+    if sys.version_info > (3, 10)
+    else _text_encoding
 )
diff --git a/lib/zipp/glob.py b/lib/zipp/glob.py
index 69c41d77..4ed74cc4 100644
--- a/lib/zipp/glob.py
+++ b/lib/zipp/glob.py
@@ -1,7 +1,6 @@
 import os
 import re
 
-
 _default_seps = os.sep + str(os.altsep) * bool(os.altsep)
 
 
@@ -28,7 +27,7 @@ class Translator:
         """
         Given a glob pattern, produce a regex that matches it.
         """
-        return self.extend(self.translate_core(pattern))
+        return self.extend(self.match_dirs(self.translate_core(pattern)))
 
     def extend(self, pattern):
         r"""
@@ -41,6 +40,14 @@ class Translator:
         """
         return rf'(?s:{pattern})\Z'
 
+    def match_dirs(self, pattern):
+        """
+        Ensure that zipfile.Path directory names are matched.
+
+        zipfile.Path directory names always end in a slash.
+        """
+        return rf'{pattern}[/]?'
+
     def translate_core(self, pattern):
         r"""
         Given a glob pattern, produce a regex that matches it.