I suspect that the standard DOOP uniform isn't necessarily anything like what Zapp Brannigan chooses to wear. After all, he is a lecher, braggart, and narcissist.

This is obviously a combat uniform instead of a dress uniform, but captains of modern naval ships don't wear dress whites while on deck anyway. And the basic styles and cuts are the same, just finer cloths are used with more ornament (braids, brocades, etc).