You can find the main thread (for suggestions, voting for the next round, and general discussion)
Now for the match up.
The Mongol Horde
The Mongol Horde spread into the largest empire ever known to the Earth led by the brilliant and ruthless leader Genghis Khan, conquering nearly all of the known world at the time. Genghis Khan's mongol horde was the entire of nearly all the Mongolian tribes united and they used some of the most cunning battle tactics known at the time. They used psychological warfare and had in-depth scouting (as seen in their European invasion) allowing them to know everything about the land they were invading as well as having it mapped out. The mongols were the primary reason for the spread of the Black Plague throughout the world. Their weapons of choice include: The Mongol Bow, A Sword (a slightly curved Scimitar that was used for slashing, cutting, and thrusting), they used siege machines capable of being made on the battle site, and they used their own prisoners as a 'human shield' to protect their main army from the initial attacks.
The Zombie Horde
The Zombie is an animated corpse brought back to life, this myth originated within Africa, as well as the Epic of Gilgamesh, and has a hence then become a big figure with popular culture. The often association with zombies is that when they bite a human they will become infected and also turn into a zombie, hence starting a zombie apocalypse. They are often depicted as being slow moving but also massive in number and faster when they see flesh they would like to eat. Their only notable weapon is their own body and their teeth, however it becomes extraordinarily deadly when there are 100s of millions of them out there seeking flesh.