"We have been outsmarted and nearly killed by a flower. We are never speaking about this again."
Yeah, I think if Red Robe were anyone who actually knew Zorian, he would have noticed by the point of the Aranea massacre that Zorian's activities have been varying from one reset to another without the difference being caused by RR's or Zach's actions. That by itself would have given away that Zorian is another looper, and RR would have killed him in his sleep.