1) If the code is uncompleted, how can we help ?
2) Why to use tasks when you have events ?
3) Indent your code properly.
4) Your set_task usage is wrong, you have to use "b" flag to make it repeatable.
5) No need to return PLUGIN_CONTINUE.
If I understood right, you just want to check when Zombies/Humans win so you can display a HUD message ?