Breeding passable mutations, and not sure how exactly what you can breed with without reducing your chances? Here's the list of currently confirmed 'roll' orders of mutations.

Basically, whatever appears first will first get a 'roll' on the cub, kinda like a dice roll. If it's successful, the cub will get that mutation, or roll further for the type of mutation(if applicable), but if not, it'll move on to the next one in the list.

Tigon/Leopon > Piebald > GMO/Lion Meat/Lion Scrotum > CRB > Fertility > Primal

Currently missing/unplaced in the list:
Overgrown Fur

This list basically means you can breed a leopon with anything without worrying about losing chances of getting a leopon. Keep in mind that using a CRB could still kill the leopon in your current litter, although it will not decrease your chances of getting a pon in the next litter.

Note that cubs are generated at conception, not when the cubs are born.