In order to use x and z you must have abilities with those as the hotkeys, and when that ability is cast do w/e to the cam.
For arrow keys use the event A player presses a button.
Create a unit with two abilities -- Rotate Left and Rotate Right. One should have the hotkey Z, one X. Using the event "Unit starts the effect of an ability", detect when it uses Rotate Camera Left, then turn it left, and vice-versa for Right.
I think that the only keys that can be assigned as an event in GUI are all four arrow keys and esc. (thats only if you use the Player - Skips cinematic)
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.