The Zend Framework is well engineered PHP code, but kind of takes an À la carte approach to the whole "framework" thing. This gives you more control, but it can be overwhelming to a newcomer and you may ended up implementing a lot of things the framework could have done for you, if only you knew they existed. It's a great approach for general software projects, but it doesn't sound like you're reinventing the wheel here.
Cake and Code Igniter are two general MVC PHP frameworks that come-up a lot. They're not as deep as the Zend Framework, but they do provide a decent standard way of routing between URLs/controllers/views, and a simple but good-for-most-cases ActiveRecord/CRUD style model (don't write SQL, just call create, retrieve, update, and delete methods on objects that are semi-auto-generated from Database tables). Cake is, in a lot of ways, starting to show it's age. There's a lot of, um, "lowercase crud" hanging around the codebase from the "Let's make an OO framework in PHP 4" days. Still a worthy framework, but if I were starting from scratch I'd go the Code Igniter route. It's probably worth mentioning that Code Igniter forked a few years ago into Kohana.
All of that said, it sounds less like you want an application framework, and more like you want a CMS that will get you 75% of the way there and then have a good environment for you to build the remaining 25%.
Drupal has some really clever procedural code to give you an OO like environment, but it's definitely NOT MVC in the traditional web application sense. The flip side of this is Drupal has a ton of modules for performing common CMS like tasks. There's also the drake module that will let you embed a PHPCake application in a Drupal site. I used Drake a few years ago and it good enough for our needs, although it looks like the project has stagnated a bit.
I've never personally used Joomla, but I've heard their module system is MVC based and I remember being impressed when I looked at the 1.5 code-base. Like Drupal, there's a ton of third-party modules that will help you do what you need to do. It's probably worth looking into their docs and see if anything draws you eye.
Finally, Concrete5 is a relative newcomer that's a CMS/Framework hybrid. While it's not as old as Drupal and Joomla, is has a growing community behind it and offers a clean MVC framework for module development AND a general url/route/controller/view MVC framework (called "single pages"). They're kind of model/ORM agnostic, but there's nothing stopping you from dropping something like Propel or Doctrine in place. I've only had a few month experience with it but so far it's done everything I need it to and hits that sweet spot of well-engineered but loose enough to get things done.