How do zombies win in Last Night on Earth: Timber Peak?
I don't actually own Timber Peak so I can't help you from experience but I did find the following comment from this post on BGG relevant.


  I found that zombie tactics in TP are different from LNOE. Without going into detail, I'd say the zombies require a bit more subtlety than in the earlier game.


So to answer your question: If your gaming group is really use to vanilla LNoE they may need to adapt a different play style for Timber Peak. 

The rest of the thread on the above link might also help answer your question.