Sorry for the delay.
Looks like I'm a bit ahead of you in that I too have been recently learning OOP, and likewise - now I am grokking mvc, have decided to use a framework also.
Now I stayed away from the ZF up till now, becuase it seems to be being worked on so much. I looked at a couple of frameworks - and went for codeigniter.
This isnt the purest oop framework, but I have used it on a couple of projects and I am very comfortable with it. Of the others Cake looks as though it has the most zealots following it, AND I saw a job advert that mentioned it...
I work on Win32 a lot, with IIS, and from what I have read there is dependency in ZF for mod_rewrite on one of the controllers. Now maybe I can work round that, but my next project will likely use Cake.
CI leaves some things to be desired, but thats how we learn, right?
For a fuller discussion search this forum for "igniter" and you will see plenty more pros and cons. See this Framework Comparison Chart.
But honestly if you intend to stick with it - try and post that ZF question on a ZF board.
The importance of seperating your application into "layers" is probably the most fundamental thing to learn.... 2 or 3 books, and a year later, the penny finally dropped with me.
I wouldnt say that using CI as I do has done this for me, but I do understand what I want to happen.