Ralph Schindler has put together a guide for compiling gearman on Zend Server CE (or really anything for that matter).

Zend Server CE for Mac (as of this writing), comes compiled as an i386 executable only. This includes the PHP binary, php library, and apache binaries that come shipped with ZSCE. While ZSCE works great out the box with all the provided extensions, you might find that you want some additional 3rd party PHP extensions compiled/linked into this stack. That’s where things get a little confusing, and in this post, we’ll look at how to install the gearman extension.

Ralph gives you all of the commands and changes you'll need to make to get gearman compiled and ready for use on your Zend Server instance. The end result is a PECL extension that can be used as you might need.