Minecraft wiki entry for Villager_(old), associated text: Zombies will try to find and attack villagers within a 42 block radius (even when the villager is invisible), and will attempt to break down doors. Zombies will only successfully break doors if the difficulty is set to hard, though only a fraction of zombies spawned in hard mode have the capacity to break doors. This also applies to zombie pigmen if they path find through a door. Villagers will run away from zombies, sometimes hiding in houses. The villager's only "natural" defense are the iron golems, which attack nearby hostile mobs.