Yeah, zone is way to effective in this game. All I run is a cover 3 stunt or cover 2 stunt with a qb contain if playing against a running threat. My biggest problem is how unstoppable AI is. Even on All-Pro their QB has a completion % > 70 (maybe 80) and their defenders blow through your o-line. Then on top of that they have an insane ability for play recognitiion. I created a playbook that uses 5 formations (each containing over 20 plays) yet they easily identify what I am running. I only play vs other players now. Still fun, but incredibly annoying.