In this new post to the Zend Developer Zone they point out a tool that allows you to create Zend Framework models directly from a UML2 model.

BOZA Framework is a conceptual instantiation of the Model-Driven Development (MDD) paradigm that aims at shifting the abstraction level from code to models. BOZA Framework comes with an integrated Eclipse-based toolset that allows developers to automatically generate a substantial part of the application source code. All you need is draw the UML2 structural model of the entities and their interrelationships within your application.

The generation scripts create the models, an admin backend, a database scheme for import and a working setup environment ready for additional development. You can find out more about the product here.