I just think its weird that the plants want to protect the humans now, especially since humans eat plants. In the first game (original PvZ) the plants needed the humans since they were essentially planted in the ground and were not sentient beings. now the plants can take care of themselves, can run around, jump, make noises, etc. When I go to Chomper's pizza the menu has plants for consumption as well as dirt and minerals. This means that either the humans go to Chomper's pizza and eat the vegetables/seeds on the menu and the plants also go to chomper's pizza and eat the dirt/minerals. OR the plants are the only customers and the eat the dirt/minerals as well as other plants (cannibals)?
Anyway I find it weird the humans want protection from the zombies because they want to eat them yet the plants would probably be better off siding with the zombies for two reasons. 1 the plants would no longer be eater 2 this would give the zombies more brains since the humans lose some protection.