The first place is actually in the code base.

Zenoss includes the code documentation in the actual product. To create and build an HTML site that will display the documentation:

From your Zenoss instance, while logged in as the zenoss user, run the command

zendoc

This creates a $ZENHOME/zendocs directory and builds all of the docstrings into an HTML file system that allows you to access the zenoss code documentation in HTML format. Just click on the index.html file

The complete documentation is also available on the zenoss website from:

http://www.zenoss.com/community/docs/zenoss-api-docs/