Unfortunately, the Z editor only makes multiplayer maps, but the excellent Antares' XP patch does mention the possibily of creating proper single-player maps:
Apart from the fact that the site is in russian (direct link to the file is this) the direct link is broken. Does anyone own this little utility, or haven't I been able to search properly?Creation of new single-player map
Z95 has its own map editor called ZEditor. Unfortunately it was developed only for creating multiplayer maps. But using our new patch you can make even singleplayer maps! After creating and saving new map, it is saved in folder like "level??" where "" is a letter from "a" to "f". To be able to load such map from singleplayer you must rename this folder and file "level??.exp" in that folder to "level**" where ** is a number from 97 to 159) for example level100 and level100.exp
Than you must use special utility ZTool from BallWin, to place starting units on map!