When a player enters after the game has already started, 500 points will be added for every 5 rounds, i.e. When the game ends I will automatically restart without having to go out and come back in. You can find the source code of all this mods here Zombies Simple Mod Feature

If you don't know how to make the mods, just take the compiled file and put it in the correct folder. Each mod will be composed of two files, one compiled and one not compiled. Just take them and put them in the correct folders and you are done.

Here I leave you some mods that you can put directly on the server to play with your friends.