No wait, that's these little guys:
OK, to be fair, they're only 1/2 jackasses - they're 1/2 donkey, 1/2 zebra. They're Zonkeys - or zebrasses, zebronkeys, zeasses, zeedonks, zebadonks, zenkeys, donbras, donbris, or deebras... not one of which is a technically correct term for them. The better terms, to those who claim to know such things, are zebrinnies, zebrulas, and zedonks. A zebrinny is the offspring of a male donkey and a female zebra; a zebrula is the offspring of a male zebra and a female donkey; a zedonk is the offspring of any zebra and any donkey - or, just generically, they're all zebroids (crosses between a zebra and some other horse species).
The reasons such crosses are possible is that donkeys (Equus africanus asinus) and zebras (Equus quagga, Equus zebra, or Equus grevyi) are both closely related members of the horse family. Even still, these mixes are rare. But they do occur where the two species are kept in close quarters or when people decide that a cute hybrid sounds like a fun idea. Like mules (crosses between horses and donkeys), they are genetically sterile due to an odd number of chromosomes disrupting meiosis. The trouble is that donkeys have 62 chromosomes while zebras have anywhere between 32 and 46, depending on the species. Somehow, the weird combination allows for viable gestation and development, but not viable sperm or eggs to continue the next generation.
There is one recorded case where a zonkey has successfully bred - at least according to Charles Darwin. In The Origin of Species, he reported a case of a zonkey that mated with a bay mare to produce a horse-zebra-donkey hybrid. Unfortunately, no such successful pairings have been recorded since... It would have been fun to try and name them. Zehordonks? Hordonkbras? Donzeeorses?