Do you shave the area where you see these "zits"?
I know I can't shave certain areas down there... because I will get a horrible irritation.
Otherwise, I coudln't really tell you what is going on.
Uuumm... do you wear biking shorts? Do you wear underware under your biking shorts? Do you use body glide on these parts (before the irritation?).
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"