Z Malloc error
From DoomWiki.org
Z_Malloc is an exiterror that occurs whenever an overflow in the Doom Engine (whether it be number of things, linedefs, etc.) exceeds a designated heap size for the game. The DOOM engine tries to render everything but overbounds itself on it's allocated memory array, and disgracefully crashes.
NUTS.WAD[1] is an example if ran on vanilla (crash at 63047+ bytes) or chocolate doom (crash at 262000+ bytes).