Making Zombies prior attacking buildings if they can't reach nearby units?

[qbrtux]

I need help with making an AI or so for my zombies in a map, via the object editor I can make them go for buildings (or walls) before units, but I do not want them to attack a large heap of buildings when there is nearby archers to gnaw on.

I neither want them to stand around, tanking arrows just because there is a house in the way, they should start tearing it down to reach the archers.

Appreciating help.