Corona ointment for diaper rash?

My baby has a pretty severe yeast diaper rash. His pediatrician has seen it 4 different times, prescribed 2 creams, and nothing is working. We don’t use wipes (sitz baths only), frequent diaper changes, air dry, plenty of diaper free time, and have tried every diaper ointment we can find.

I had a few people suggest corona ointment that is actually meant for horses. Has anyone used it? Is this safe? I can’t find the ingredient list online.