It is a Zombie riding a Wither Skeleton Skull.
Have Fun!
Note: Minify the command to avoid issues :)
Death Rider
Control Panel For Your World or Server
OPish Coke
Small Prison Kit!
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)
genessee
genessee
darkknight3227
galbby5
deadpoolbadhair