Some years ago one zoo in the UK sold another a surplus miniature pony for the pregnant zoo.
When the second zoo discovered the pony was pregnant, they called the first zoo.
The first zoo's response: She can't be. We don't have a stallion on the premises.
The foal came out with stripes.
Apparently, the first zoo didn't consider that she'd got in with the zebras...
A zorse is a zebra horse hybrid. Zorses are generally small and often lack any kind of prominent wither. Like zebras (which are, after all, wild animals) they're known for being hard to train - although zorses have successfully competed in the show ring both under saddle and in harness, over fences and even in dressage. They definitely resemble horses more than zebras.
However, zorses are readily distinguishable from pure horses because they always have some degree of striping. Specifically, they have black stripes on a base of a familiar horse color, such as this bay or dun zorse:
(Source: Kumana @ Wild Equines).
If the zorse has pinto markings, the stripes do not carry on across the markings and they can be more subtle, but a zorse will always have stripes.
Sometimes the offspring of a zebra and a pony is called a zony.
Zebras have a much different chromosome number from horses - horses have 64 and zebra species range from 32 and 46. Like mules, zorses are infertile. Also, because of the much greater chromosome difference compared to horses and asses, zebra hinnies are almost never produced. When they are, they seldom survive to adulthood. Also, zorses are prone to dwarfism.