Zend

If I understand correctly I should already have Zend installed since it is bundled with PHP? Or do I need to download and install Zend myself?

I also see other refrences to ioncube, which one do you prefer?

Yes, you need the Zend Optimizer installed. You can download the encoder test script here and check for compatibility

With regards to preference... none, really. We use the ionCube version here, but both perform as well.

Cheers