Going out on a realshaky (as I'm sure Babs would say) limb here and saying that D's linemates may be having at least a LITTLE effect on his ability to score lately at ES.
I do think that Z hasn't play well lately, and when he's off his game his line is invisible on the ice. And I'll even agree that every team hits stretches in a season where goals are hard to come by, but at least try to throw in a few coaching adjustments here and there to address the problem.
Typically when a team isn't scoring, the coach is changing the lines to find a spark somewhere and see if a new combination could get hot... seems rather passive to chalk it up to "oh well guys, you know how the game of hockey is- everyone hits a dry spell during the season. So we won't make ANY significant line changes to get us going, but instead keep doing exactly what isn't scoring at the moment. Sounds good, right? Now get out there, play realgood, be hard on the puck, and keep competing!!"