i dont think zombies can be turned back, only ghosts. i could be wrong, i've never made a zombie. lol tell me how! but seriously, i've never heard of zombies turning back, i think they just live with you.

Alright that's the easy part.
1. First kill your sim. Then press Ctrl+Shift+C.Type in unlockcareerrewards.Then go to
career rewards and pick the strange telephone.
(make sure that your sim knows the dead sim).
2. Click on the phone and click "Call Grim Reaper".
3. When you choose your sim it will appear a bar.
4. Move the bar at least 1.800 simoleons.
5. Grim Reaper will start complain.
6. Your zombie will eventually appear!
7. Have fun with your new creation!!!

Up there^^ it tells you how to make zombies, but you can't get rid of them.

If you have made a zombie you need to:
1)kill them
2)Click ctrl,shift C then type in Motherlode
3)click on the grimrepers phone and give thee full amount of money
and then they will become sims again