The cross-breed of a horse and a zebra is known as Zebroid (and zorse), not Hobra. Zebroids have been bred since nineteenth century. You'll be glad to know that even Charles Darwin wrote about Zebroids in 'On The Origin of Species'. Afterwards, many writers from 19th and 20th century also wrote about Zebroids. It's difficult to say that do zoo authorities still breed Zebroids because as soon as one of those breeds is born, biological departments take the matter in their hands. If you are interested in knowing more about Zebroids, please refer to Reference URL provided.