One day, there was a player. A player playing during a storm. The player stopped to see a green horse.
“Weird.” he thought as he went towards it. He realised it was a zombie horse so he put on a zombie head.
“Woo hoo!!!!!” screamed the player, riding around on the horse after putting on a saddle. Then he stopped and thought.
“Zombie Horsey, I need to get my diamond pickaxe”
He rode the horse to the house and stopped. He went inside and the zombie horse saw through the window that he was providing pin codes to get through an enormous mansion just to get to a few tools. He had taken off his zombie head as well.
“I suppose they are diamond tools, and I always thought he wasn’t exactly a zombie.” thought the horse.
Then a zombie came towards the zombie horse, enraged.
“How dare you run away!” shouted the zombie. The zombie hit the horse twice with an iron sword.
And that is why zombie horses don’t let you ride them in Minecraft.