They don't really have excellent chemistry. Kreider scoring 50+ was due to him absolutely feasting on the PP. That won't change if he doesn't play with Zibanejad at ES.
The 2 of them have gotten caved 5v5. For all the hate that Panarin and his line got during the playoffs (all warranted btw) Kreider-Zibanejad got smoked even worse at ES - It was ignored because Zibanejad was really productive otherwise and Kreider scored some timely goals. The reality is, they've become the epitome of one and done in the OZ 5v5, which is something we need to get away from (and they aren't really good enough cashing in on the rush to justify keeping them together.
The bromance makes for good vibes and msg network fluff pieces, but their chemistry died the second Buchnevich was traded... because KZB was really more about how well Z and B worked together. Kreider has actually performed better away from Zibanejad too. He and Chytil have always crushed it when they've been deployed together and I'd actually like to see what he looks like with Trocheck as it may influence/force him to get back to doing some of the other things that he can do really well when he wants to, but tends to get away from when he's playing with Zibanejad and that way you don't have to break up the kid line, who to this point, is the only line that can actually create offensive off of the cycle.