Spigot plugin: Zip your world!
With this plugin, you can create a zip-file from the world you are currently in.
Downloads are available at Releases. Just click on WorldAsZip.jar at the latest release.
Go into the world you want to save as a player and make sure you are opped. Then, type /worldaszip to save the world as a zip-file. You can find the zip-file at YOURSERVERPATH/plugins/WorldAsZip/WORLDNAME.zip. Please note, that Overworld, Nether and End are separated! At default world names, world.zip will NOT contain the nether or the end!