This video's immortal. It still cracks me up. And this glitch can only happen to mages. I think it's what happens when they reach 0 HP and cure themselves at the same time. 'Cuz I "killed" a mage in GvG awhile back and his sprite appeared to be fainted, but I saw him sliding around the ground with the Heal effect appearing on him. So, yes, zombies can cast spells. It just doesn't show the casting animation. Just the skill animation.