You actually had always been into the idea of animal transformation, especially horse transformation. While Zebras were different, you couldn't help but feel aroused at the idea of mating with this mare and being turned into a Zebra stallion. It just made you more aroused and when mixed with the smells coming from the mare's backside you just became more and more aroused as your cock grew longer.
"So what do you say big boy?" She said and leaned forward over the bed, her tail swishing back and forth to show her vagina winking at you. "Come on, I'm in heat, I want to bear your foals you handsome Zebra stallion stud."
You couldn't hold back anymore as your growing Zebra mind smelled the pheremones as your cock finished its growth and you climbed on her back and pressed the tip of your cock against her entrance and thrusted into her causing her to let out a loud moan. You started to thrust in and out of the Zebra which made your transformation speed up.
First your face started to push out more into a muzzle as your fur spread over your body. As you thrust in again your bones shifted and your legs and arms became equal length with one another. You were filled with euphoria as your body was transformed and the mare's moans turned into brays as she moved with your thrusts.
As you kept thrusting your mind kept drifting as you gave into your new animal instincts. Your face finally pushed fully out and your ears migrated to the top of your head as you thrust in one last time and brayed loudly as you came hard into the mare's vagina before she clamped down and drew out as much of it as she could.