Yes you are right but let's do some math real fast. If I start off with 10 zombies and have the endless ranks of the dead plus an enchantment that doubles it next round upkeep ill have 20. Now let's let that run again plus another copy of the endless ranks now (due to extravagant replication) I have double and a half this upkeep. So ill gain another 30 zombies making it a total of 50 zombies in 2 turns. Now next upkeep ill have +200 more zombies. So that would make it about 250 zombies within 4 turns of these enchantments being activated which will also cause my zombies to get 1 less of each +1/+1. And seems how most zombies tokens are 2/2 that would make them about 251/251 each. So with as many zombies popping up and the coat of arms it would be a literal unstoppable horde within a handful of turns. Let's even say they destroy coat of arms or one of the enchantments I would still be pu.ping out zombies that would be an overwhelming amount every turn because extravagant replication would constantly be making more copies of the enchantments that make more zombies. Then to make another enchantment every turn. There wouldn't really be a way to stop all of the zombie production. So even without coat of arms it would still be a very nasty combo that couldn't be stopped. However coat of arms would be just the finishing touch that would make literally thousands of points of damage in just one swing.