summon Zombie ~ ~1 ~ {Riding:{id:Slime, Riding:{id:MushroomCow, Riding:{id:Creeper, Riding:{id:Villager, Riding:{id:Skeleton, Riding:{id:Spider, Riding:{id:Chicken, Riding:{id:Pig, Riding:{id:Cow, Riding:{id:Sheep, Riding:{id:PigZombie, Riding:{id:Enderman,Riding:{id:CaveSpider, Riding:{id:SnowMan, Riding:{id:Witch, Riding:{id:Bat}}}}}}}}}}}}}}}}}