Hey, do you mean sudocrem? (that's what it's called in England - I'm assuming your American as you said diaper
I've been pretty religious about this stuff for a few years. As you said, it contains zinc, so I feel it has to help somewhat. Plus on the tub it even says 'helps with acne' or something along those lines.
As I tend to suffer with red marks a lot, I like to use this to make them appear less red (I like to think of it as me putting on make up, as I'm a guy I'd have no idea what to do with make up lol)