ZDOOM is a port of the DOOM engine by Randy Heit. Please refer to the ZDOOM documentation on how to use the new features. Most of the HEXEN documentation also applies to ZDOOM in HEXEN mode.
See the ZDOOM.OPT or ZDOOMHEXEN.OPT files if you need to add new COLORMAPS or modify the LineDef types.
There are various other ports in progress so check our website and get the links to the Doom Editing community.