Seconding the previous two wise gals posting ahead of me. Get the saddle fit issues taken care of first. No amount of topical cream can solve problems with saddle and shorts fit.

That aside, I had some spectacularly unpleasant results with diaper rash cream containing zinc. Zinc is a natural antimicrobial agent, and it completely nuked the natural protective flora that I try to nurture down there. This led to problems with yeast infections, cracking, bleeding, etc. Occasionally I'll do some spot treatment with zinc on a zit or saddle sore, but now I generally avoid it.

Water-based lubricants work well for me. Also, if I'm feeling borderline, an over-the-counter anti-yeast cream (generic miconazole) also works great as a lube. Both of these wash out just fine.