Lets go with the romantic option
I like Zucc, I really hope they work something out. I think there is a deal to be made, it's guaranteed money for the most part, minus escrow and possible work stoppages.
If he'll settle for 5Mx4 that is 20M total, add the 5th year and it's 4Mx5 and still 20M total.
Since I think 4M is a little low ~4.25M x 5= 21.25M makes more sense, if I were him though I ask for bonus money in the year where a work stoppage is possible (both sides have opt out Sept 2019, bonus money would be paid prior to Sept) which would make it almost guaranteed money minus escrow should the players side come up over the 50% split. If he gets that bonus money that year and there is a lengthy stoppage he may end up actually making more than a player who signed a bit more expensive deal but is paid in salary that year. Rangers have money, cap space is going to be their issue.
Now I think he could get more than that on the open market, he may even get that total over 5 years to be closer to 25M, so it would mean he is leaving about 3.75M on the table over those 5 years but he is doing so to stay with the Rangers which if he is being sincere about wanting to stay seems like a relatively small amount (750K per year) to give up to do so. At 4.25M per I think the Rangers may even give him a no trade for the first two years, from there maybe even a limited no trade, so he does not have the chance to end up somewhere he totally does not want to be.
To me that is a pretty decent compromise. We'll see what they come up with but I'm still a little worried the Rangers may end up going MSL over Zucc short term if he really pushes for more than something like that.