Interesting question! In order to find out what a “zedonk” is, let’s start by picking apart the compound word. “Ze” is short for zebra and “donk” abbreviates donkey. Instead of calling the animal that results from a cross between a zebra and a donkey a “zebradonkey,” it is called a “zedonk.”
With that settled, now let’s take a look at how crossing two different animals to create a new animal is possible. In general, animals, in this case, mammals, mate with like animals to continue like kind. However, there are a few exceptions to this generality when the animals are similar enough to produce live offspring. One example that is pretty familiar is dogs. Different types of dogs can mate with each other to produce new types of dogs with the desirable characteristics of both types of dogs. The new dog is often given a cute name that mixes the names of both animals. The labradoodle(labrador and poodle), cockapoo (cocker spaniel and poodle), and puggle (pug and beagle) come to mind. Similarly, donkeys can mate with horses to produce mules or hinnys and with zebras to produce zedonks because they are similar enough.
Despite similarities between animals that allow new offspring, there is an important difference between reproducing dogs and reproducing mules, hinnys, and zedonks. The offspring of dogs of different kinds are fertile, meaning they can continue to reproduce new offspring. However, mules, hinnys, and zedonks are sterile, meaning a new generation cannot produce offspring.