[Zope] Zope Development: Taking the Next Step

I've been using Zope for about a year or so. In this time, I've become thoroughly comfortable with user-level development -- I've done decently interesting python scripts, page templates, etc. I've come to really understand, however, that when it comes to the next level of Zope development, I'm not really sure where to start. Having had to take a look at some Products recently and tweak them, I find that while I can tweak things sometime, I'm certainly ages away from, say, being able to create my own Product or understanding even how they work. Is there some sort of decent way to start delving into this that doesn't involve "just read some Products and figure out what they're doing"? -roy