When a zombie virus infects a monkey it dies and becomes a Zonkey! Then this living-dead zonkey infects the rest of the monkey population, resulting in the apocolyptic end to the world as we know it. The only way to kill a zonkey is to shoot it in the head, decapitate it with a big rusty shovel, or run it over with a big tank or something.
P1: Holy SHIT! There's Zonkies all over the fucking place out there!!!
P2: A zebra monkey hybrid?
P1: No you idiot, that's impossible-it's a zombie monkey!
P2: Oh shit, that God Damn Zonkey just bit me in the crotch!
Like the term "donkey", it refers to a bad poker player. The zonkey, however, makes especially flashy poker moves or uses language to indicate they "know" the game when it is just a matter of time until they "zonk" away all their money with their poor play.
The term is based on the animal called a "zonkey", which is a cross between a zebra and a donkey.