[Zope] Editing the z2.py File

Hi; I have my own server with virtual hosts. I'm going to build a large Web site on this server with Zope as the base platform. I intend to build more on the Zope platform, but already have several sites built without it. My question is, how do I edit the z2.py file in such a way that I can call up certain virtual hosts and not others through port 80? Also, can I build the equivalent of a doc root off of the Zope root such that Zope could act, in effect, as a virtual host, or do I need to create a separate instance of Zope for each domain? TIA, BenO