When a job has Zend Framework as a requirement they mean server side Zend, not the IDE.
However, if you've never programmed in PHP OO, Zend Framework may be a bit too much too start with, because it's extremely big and you need to set up a lot of stuff to even get started. (In my opinion Zend is too extensive for most any project, but that's just my opinion).
As RonnanR said, you may want to start with basic PHP OO. Read some manuals, view some videos on YouTube (which there probably are) and then get your feet wet with a more basic (but still powerful) PHP OO framework like Yii, CodeIgniter, Symfony (preferrably 2) or Cake (also 2).
If you insist, you can get Zend Framework at http://framework.zend.com/