A hybrid animal. Zebroid is the slightly less silly name than zorse for what you get when you cross a horse and a zebra. Actually, zebroid is the generic term for a zebra/horse or a zebra/pony or a zebra/martian, for all I know. But if you say zebroid, people are going to think zebra/horse. Zony or zeony are reserved for zebra/ponies. See if you can guess what a zebrass/zonkey or a ze-donk/zeedonk is made of.
Like all human created hybrids, zebras and horses will not mate in the wild, but if you keep them alone together in a cage long enough, hey. The usual pairing is a horse mare and a zebra stallion. The offspring are sterile. I point this out because not all hybrid animals are sterile, like many people think. Dogs and wolves, or wolves and coyotes, for instance, can produce fertile offspring. They are considered to be separate species because of actual breeding behavior in the wild, and physical differences.
The adjectival form of the word is "zebrine". A zebroid will generally be black and reddish brown or grey in color, with black stripes on the body that fade somewhat down to the legs and the head. Some of them may have pinstripes all over their body, instead. They have a wiry mane, like a Roman helmet's plume, which varies in color.
Zebroids make noises like Zebras, but can be saddled and ridden like horses. But not by anybody: Zebroids are smaller than horses, more around zebra size, and are harder to train.