Let's take a quote from Wikipedia about zebroids.
Donkeys are closely related to zebras and both animals belong to the horse family. These zebra donkey hybrids are very rare. In South Africa, they occur where zebras and donkeys are found in proximity to each other. Like mules, however, they are generally genetically unable to breed, due to an odd number of chromosomes disrupting meiosis.
First, if I understand meiosis, the resulting cells don't actually end up with half the number of chromosomes, but closer to a full set of halves of chromosomes. How is the meiotic process disrupted?
A donkey has 62 chromosomes; the zebra has between 32 and 46 chromosomes.
Apparently this difference doesn't obstruct producing (infertile) offspring. How comes the process of recombination of such vastly different number of chromosomes in gametes is viable? What happens to chromosomes that don't find their 'pair'?
Horses have 64 chromosomes, while most zebroids end up with 54 chromosomes.
54 is an even number. How comes zebroids can't just normally produce fertile offspring with other zebroids of the same number of chromosomes?