Removed zoom functionality is about the proof of concept full zoom that was in hildon-desktop. One could zoom in and out the full screen wit Ctrl+Shift+S and Ctr+Shift+D, but there were several issues with it so that it isn't useable.

About your graphical artifacts, I fear you've got a hardware problem there, the render code itself only changed for tasknav. But I also remember having weird artifacts from time to time on one of my devices, a reboot usually got rid of them though.