Disagree - I know very little of Val-Zod, but what little I know of him paints him as being different than Clark Kent. Val-Zod seems to be his own unique character, just like Clark Kent is. So no, I doubt they're interchangeable, and I don't see one existing as some way to argue for race swapping. The opposite in fact. If Superman being black is important, use Val or Calvin instead of Clark.