Formerly, Zope required its own extension mechanism (called "Zope products"). Nowadays, it can use standard Python packages for extensions. Any Python subpackage of the (so called) "namespace package"
Products available for your Zope instance is treated as you know this from the former "Zope products". You can use the ZCML directive
five:registerPackage to allow any Python package to be treated as a "Zope product".
The Python documentation contains documents related to packaging/packages.
setuptools to set up and manage (e.g. install, publish, develop) my Python packages. It can publish packages on PyPI, but this is not necessary; it can also install (in a development or production mode) packages locally. I am sure you will find documentation searching for "python setuptools".
I suppose you have already read the Zope 4 documentation. You have learned there that there are different kinds of Zope 4 installations (e.g. "virtual env" based or "buildout" based). How you exactly provide Python packages for your Zope installation depends on the installation type. I use virtual env based installations for Zopes which likely have a short lifetime and "buildout" based installations for Zopes likely to require maintenance for many years ("buildout" facilitates version evolution for the many packages which typically comprise a Zope application).
You will find many product examples on
setuptools related file is
setup.py. Do not install those examples (the installation will execute but not install
setup.py); instead download the source, unpack and explore.