A recent tutorial (screencast) has been posted to the ZendCasts.com site looking at creating custom Zend_Form elements when you need something more than just the usual, simple elements.
This video should help you build your own composite Zend_Form element. We’ll be building a phone element. The phone element will have 3 textboxes, one for geographic location, area code and local code. In the following videos will add a custom cell phone validator and some ajax validation.
You can grab a copy of the source if you'd like to follow along or you can just look around the repository to find the source for this and other great lessons from the site.