I created a superflat world to see how a zombie break a door and attack villagers, and then I built a floating micro-platform (pictures will be attached in "Attachments") that disallowed zombies approaching villagers by walking on ground directly.

But when I put a door at middle and spawned a villager and a zombie in two sides separately, it's strange that the zombie did nothing (sometimes also shaking its head) instead of breaking the door! It's also confusing that zombies beneath the villager yet had the normal action of attempting attacking the villager. It seems that the zombie's AI have some errors to be fixed.

And also, the texts above is the reproduce method.