Well, from a contrarian point of view, when people start talking about ZB at 200 at this point, it's time to start scaling into a short position. Reminds me exactly of the oil trade, when it hit $140 and people started coming out asking when (not if) it would hit $200.
Could be more upside on ZB, who knows. But when this thing turns around, between the sellers running for the door at the same time and the shorts piling on, I expect the reversal to be as vicious as the one we've seen in oil.