zend optimizer and ioncube only have 32bit versions for windows. So, no native 64bit support for windows 2008.
In order to install zend and ioncube, one need to do a little more work which is to hook 32bit version into IIS7 through some methods. How to do it? I don't know cause I haven't done so yet. Google around and you will see one or two skecthy methods where people mentioning how they got it to work. Even zend and ioncube site doesn't have proper tutorial to install their 32bit software in 64bit windows.
one example :
http://www.viart.com/forum_topic.php?thread_id=1745&page=1#message_form
I am not going to risk installing it on customer's live system. Nor have I resources to test it on a test system.