Do zombies know how to open doors? Hmmm... My house is defenseless against zombies, except for that it's out away from the big residence areas... so unless the cow stench in the air doesn't dilute the scent of human brains they won't think to come here. Or whatever they do to command their body parts to move.
What can I really do against the zombies? Well, in a world where zombies are real, I am a magical guy who can fry them. And Wii Remotes really slice things without direct contact, so I have a weapon too.
If it's zombes we're talking about, who want brans instead of brains, you could get a truck of Raisin Bran and leave it in a trail that leads the zombes directly to a big gaping hole in the ground where they'd never escape.