A couple ideas:
Smaller map pool, try to restrict to the maps that were originally played often in the vanilla ZM (red queen, death run, shoop da whoop) +- a few others to change it up. Are you able to put the normal ones on rotation but still have everything votable?
Advertise a ZM Community game night: In a game with a population this low, it's often easier to specify a time so that there's a higher likelyhood of enough people being on to actually play.