The mad dog Zod is the opposite. Somehow seeing no difference is pretty uncritical. If being whipped was going to unhinge Zod, you'd think he'd have gone nuts on Krypton. The Kryptonian Zod probably would have started planning another Phantom Zone escape. Hence the creation of the new personality. Well, if they insist, but no one has a right to insist that the audience must let the makers have it both ways.
I liked Zod's motivation in Superman II much much more, which was to rule. Simple but effective. Also Terence Stamp was awesome.
Zod was just Hitler in MOS. Meh.