Why is a zonkey sterile?

A zonkey, which is a hybrid between a zebra and a donkey, is typically sterile due to the differences in chromosome numbers between the parent species. Zebras have 32 to 46 chromosomes, while donkeys have 62 chromosomes. When these two species mate, the resulting zonkey inherits a mix of chromosomes that often leads to an uneven number, preventing proper pairing during reproduction. This chromosomal mismatch hinders the formation of viable gametes, resulting in sterility.