If anyone ever played the old Zombie Master mod back in the day, there's a highly active team working on remaking it (even more so than Zombie Master Black Edition or Zombie Master 2). Always looking for more playtesters/content creators, especially since the new devs have made it so easy to input your own custom content (weapons, zombies etc.). I've been working on a few maps for it, too.
Link to the discord below! Even a few of the devs from the original ZM days are fairly active on there, too.