How do i make a mob atttack everyone but the player?

Use the look at nearest (Player) task.

Add attack entity task.

Lock the code and replace

this.targetSelector.addGoal(5, new NearestAttackableTargetGoal(this, ZombieEntity.class, true, false));

With:

this.targetSelector.addGoal(5, new NearestAttackableTargetGoal(this, MonsterEntity.class, true, false));

This will make the mob attack monster entities.

Note the '5' is the tasks order so whatever number was there when you edited the code you should replace the 5 with.

I noticed that EntityMonster was in the procedure menu but not the AI task menu.