[Honestly, Zero is at a loss of what to do. More importantly, he knows at this moment there is absolutely nothing that can be done to help him. He knows this grief all too well himself and there's nothing he can say that will make a difference.
He just knows that when everything you've known has just been slaughtered in front of your eyes and you couldn't do anything to stop it--never in your life would you ever feel so alone as in those moments after the danger left and before someone arrived to help.
Zero stood behind Sasuke protectively, eyes trained on the arrival and willing him to leave him alone.]