I have Zone Manager with a pvp zone named "pvp" right?
And here's the ruleset in TruePVE

  "Mappings": {
    "default": "default",
	"pvp": "killall"
  },
  "Schedule": {
    "enabled": false,
    "useRealtime": false,
    "broadcast": false,
    "entries": []
  },
  "RuleSets": [
    {
      "name": "killall",
      "enabled": true,
      "defaultAllowDamage": false,
      "flags": "HumanNPCDamage, LockedBoxesImmortal, LockedDoorsImmortal",
      "rules": [
        "anything can hurt players",
        "players can hurt players"
      ]
    }
  ],​

Some how players on the same team can damage each other as wll. How do I add team check?

you can't. that's a plugin in itself. use https://umod.org/plugins/friendly-fire

I see. Thank you!