I'm perfectly fine holding on to DZ until the trade deadline. SOMEone will pay up then. They always do.
As RB, BRB and others have mentioned, we should also be looking to unload Girardi and Callahan at the deadline. They should both fetch massive returns then given the types of players they are, UFA or no. And honestly I don't think it would hurt the team that much given the direction they're pursuing. Neither one of those players is going to push the squad over the top, we don't want to give them those retirement contracts, and I don't think either of them has been key to this team's success one way or the other. Seriously - does anyone think this team played any better with Cally on it this year? Has Girardi been a major (positive) difference maker? You could move both, get very valuable hauls, and the team wouldn't look that much different than it does today.
Likewise, we should be looking to trade one or both of Moore and Boyle, and I'd listen to offers for Staal. (I'd also listen for offers for Nash, but I don't see it happening.) That leaves you with:
Kreider-Stepan-Nash
Richards-Brassard-Zuccarello
Hagelin-Miller-Pouliot
Dorsett-Lindberg-Fast/Kantor/Kristo
McDonagh-Stralman
Moore-Allen
Falk-McIlrath (if healthy)
Lundqvist
Talbot
Plus about 10-15 high quality assets (top notch prospects, 1sts and 2nds)
Think about it - is that squad above REALLY that different from the squad that's been hovering at .500? And have I subtracted any parts that have been prime difference makers in achieving the wins they have obtained? (Also note: that's without factoring in contributions from young guys who might be coming the other way. If 1-3 of those assets are players playing in the league right now, you can push a Lindberg, Fast/Kantor/Kristo or a McIlrath back down to HFD.)
If Slats, Gorton et. al. are smart, you can achieve a 1-year turnaround a la Philadelphia a couple of years back - and, hell, you might not even miss the playoffs! (For those who think it's vital that this team get in every year no matter what.)