Where do the zombies move in this quest?
I think I found the solution. This is from the Zombicide Black Plague rulebook, page 24:


  In case there are no open paths to the noisiest Zone, Zombies move
  toward it as if all doors were open, though locked doors still stop
  them.


Which means the zombies from 5R will go stuck themselves in the dead-end of 8V until a character opens the door (which also allows another character to snipe them from the tower 10V in the meantime).