For the English what really merks the Atzecs are guns.

I had 4 stacks full of mercenaries, each with a general, and I defeated the main Aztec force in 2 major battles. Bring over elephants, arquebusiers, any heavy cavalry and horse archers and victory will be simple. In the jungle tactics don't matter, just line up defensively, wait for them to come and when the time is right, charge. By this time yours and their reinforcements should be on the battlefield as well.

On my current campaign I'm collecting 2 units of every type of mercenary available (including crusaders) in forts around my capital. If I want every mercenary unit the English can get, I'll have to wait until 1450 or something but nevermind. It's really fun seeing every culture in the game represented on the same battlefield - and thinking of the Aztecs as they are confronted with whites, blacks, browns, guns, cavalry, elephants and artillery for the first time all on the same day.