Just holding a Korean DMZ style situation in UA would take up most of the manpower UA still has, never mind going on the offensive anywhere, and even with international troops in the country, it's going to be a challenge just to get a Korean DMZ situation to a stable point.
Given enough economic and military assistance, UA could absolutely do it.
But the biggest issue is the "enough".
Secondly, overall i think a DMZ style situation would have a lot of issues, we should not project the Korean analogy when we have a more direct one - the Donetsk and Luhansk "contact line" 2014-2022.
It does look like Russia is far more competent in leading "hybrid warfare" and "conflict below threshold of war" with generous propaganda and political fuckery, than it is in large scale, overt, conventional warfare.
We still have plenty of confusion, propaganda stories and arguing about it documented in the relevant thread on this very forum even.
Be it Ukrainian, EU or US troops on the contact line, doesn't matter, this shit will most likely happen again, possibly even more, and previous experience suggests that the quality of western politician's reactions to such scenarios (and their reactions in the many similar scenarios involving western forces in Middle East too) is generally disappointingly insufficient - and will be more so if the kind of people who insist on how great such an end to the conflict would be have any say about it.
If people who make it clear that they want the conflict to be frozen no matter what as some sort of ideological-doctrinal imperative, then the cheeky shits on the other side quite often come to the conclusion that they can interpret it that they have license to do said "no matter what" as they wish, with no fear of any retaliation meaningful enough to even suggest "unfreezing" the conflict. That in turn causes political turmoil, demoralization among civilians and military alike, and outright disarray and economic damage in the afflicted country, which is something Ukraine is going to have plenty enough issues with even if it ends the war in an actually optimistic scenario rather than this.