[Zope] Using ZClasses programmatically

Hi, can anyone point me to a good ressource how I can handle ZClasses programmatically. I walked through 2 Zope books, but they almost only say something about creating and using ZClasses in the ZMI. What I need is information how I can use the objects in my code. Would Beehive's ZClasses Tutorial by a better point to start off. Is there a way to lookup an object by it's ID like ZODB.lookupObject(ID) to get an entry point für object access. TIA Frank