Egg files are a format defined by setuptools. If you look in the setuptools documentation it notes that egg files are simply zipfiles with a particular structure and naming convention. So from a core Python perspective, you can use eggs just like any other zipfile. See the zipimport documentation for further details if you need them.

To further confuse the issue, setuptools includes some pretty complex mechanisms for adding eggs to syst.path so that their contents can be imported (there are .pth files and multi-version support, for example). Those mechanisms are part of setuptools, not of core Python. From a core Python perspective, the path handling is something you do manually.

So while I understand your confusion, I think you should understand that it is a confusion over the setuptools implementation, and how it interacts with the mechanisms defined by core Python (which are defined in terms of zipfiles). So if you feel there are any documentation issues, they should probably be addressed by setuptools rather than in the core docs.

On a peripherally related point, your comment "zipped egg files in sys.path are not found" doesn't really explain your problem very well. When reporting to setuptools, I'd suggest that you need to clarify your problem a bit better - what steps did you take, did they match the steps that the setuptools docs tell you to use, and how did the failure show itself? But as I say, that's for a setuptools bug report.