Z Expansion , Z 2014 from GOG or the one from Steam, Z for Android, Z with Dosbox and Z95 with another box like VMware Player, not to mention all its mods ...
Personally I prefer the first Z with Dosbox because I have this cd
and Dosbox bears the 2 F label : Free and Fun. At last a dos that is fully and easily customzable for game purpose !. Unfortunatelly I will never try all these ones but I wonder whether they can be connected each other for a multiplayer attempt?