I just tried the Triple Hammer using three units of conquistadores against a column of computer-chosen Aztecs. It's much harder to pull off than it looks

The buggers stuck a unit of chanting Coyote Priests outside the gates. Needless to say the varied and pretty horde (of mainly heavy warriors) effortlessly handed me my ass back (with, I must admit, admirable, sporting politeness).

On the second try, I chose the army for them using ordinary spears, archers and a couple of heavies. I still got slaughtered but I managed to take 60% of them with me.

The holding-ALT-technique doesn't seem to work half as well as it does in street battles (it's good on the open field though, I promise).

It's going to take practice.