it's possible to add ground zero & the reckoning.... to coopordie????

This pack adding has been discussed thousands of times in the past. The answer has always been a NO (Andrei knows reasons the best), and nowadays a NO is even more certain.
Just try out zomboid / angron packs (for playing angron without crash caused by grenade, you and your teammates need to patch your Q2 with a patch fix somewhere found in this support section, or you could try using 1 of the modern engines available.

It actually is technically possible to add them, but someone must inspect each of the 99999 lines of code from Coopordie's source code, check for every single change (compared to the regular Quake 2's source code) and add those into the mission packs. This happens since they use different .dll's, basically acting like mods.

Of course, you may also do the vice-versa (adding the mission packs' content into coopordie).


So yeah, unless there's someone uber-motivated to spend hours (if not days) into doing this, the mission packs are unlikely to be "added".