Reminder:
There is no Korean peace treaty.
There is an armistice and S. Korea never signed it. It was signed by N. Korea, China and the UN Command group, with the US the prominent part.
That has held up 70 yrs, tho it is likely the US reneged when it imposed sanctions on N. Korea. They clearly have not been effective so that’s a shrug.
Point being, Zelensky does not have to sign or agree. S. Korea did not and S. Korea has not ordered mass attacks across the border. If they did the US would likely bomb them for violating its signature. One could expect the same for Zelensky.
Frankly, the only real fly in the ointment is EU sanctions on Russia. The US can undo its sanctions, but the EU . . . .
Regardless, a Korea-like armistice is the direction things are going with a ceasefire in place. Russia could probably even agree to some tiny EU troop contingent in Ukraine — too small to fight, but large enough to serve as a trigger should they be killed in a Russian attack.
This is suddenly all doable.