I would be skeptical thinking there are many teams looking for more than just a few months of play from Zuccerallo, I just don't see a huge market looking for multiple seasons for Zuccarello because of 1) age and 2) his 6mil cap. I forget all the CBA details but my understanding is his extension would need to be +$6mil and I don't see teams doing giving Zuccarrello a $6.5mil 1-2 year deal at 37 years old.
Hartman, there is so much more flexibility for GMs to work with. His low $1.7 cap hit, his ability to play a role whatever the GM is looking for, he is only 29. I can see a trading team extending him for 3-4 years after that.
Not only that, even if Zuccarello was 50% retained, he would cost $3mil and some of the cup contending teams just don't have the cap space. Now, Hartman at $1.7mil, a cup contender could squeeze him in their team and more market demand = higher the price.
If I was a team trading for Hartman with zero intention of re-signing and has already made their mind up before he wears their jersey, then I would more or less agree with your assessment - 3rd for Hartman (would still lean into a 2nd). But there's going to be a large market for a $1.7mil 40-50 point versatile center/wing PKing gritty character forward (and that PPG is being conservative based on his last 2 seasons) who can then extend 3 more years of him.