You know, I think DZ being on the right side has negatively impacted both his play AND that of Moore.
Regarding DZ: we've all seen with our own eyes that he is an unquestioned top 4 defenseman on the left side and on the left side only. Unfortunately, despite having played there for over a season now, he has been unable to adjust to the right side - it seems to have neutered his offensive game and on defense, he isn't nearly as comfortable playing the body and, worse, drifts back to the left time and time again, throwing the whole defensive configuration out of balance.
Regarding Moore: he suffers from DZ's instability. He needs a stalwart, simple, defensive defenseman on his partner who can cover for him when he makes a rush. You'd want to see him making the plays we saw last year and in preseason where he rushes up to force the offense and then, if the puck turns the other way, zooming back to get into position. But, in order to do that, he needs a stable, confident, defensively sound partner who he knows will have his back. With DZ out of sorts Moore plays kind of betwixt and between and shows a similar level of shakiness, because he can't really commit to the type of game he should be playing.
Both players are much better than we've seen recently, but they've held each other back as a pair. DZ needs to play on the left side (if not for the Rangers, then with someone else) and Moore needs your basic, stable defense partner to support his game. Both will continue to struggle IMO until they're put in a position to succeed.