After the zombie enters the Death state within the animator graph, it remains there and cannot revert to any other state. The animator graph simply suspends, without linking to any new state:

Death state

The code is therefore pretty simple:

    //------------------------------------ 
    public IEnumerator StateDead() 
    { 
        //Run dead animation 
        ThisAnimator.SetInteger("AnimState", (int) ActiveState); 
 
        //While in idle state 
        while(ActiveState == AISTATE.DEAD) 
        { 
             yield return null; 
        } 
    } 
    //------------------------------------