"The problem with the plan is that the four provinces that Russia has annexed are pro-Russia, with locals who consider themselves Russia Rather than Ukrainian (over-simplification but essentially true).
"
Untrue. To put it mildly (!)
"Two area (Donetsk People's Republic and the Luhansk People's Republic - have been fighting Ukrainian government forces since 2014.
Also untrue. Those are pseudo-"republics" contrived by Russia in connivance with local pro-russian gangsters, effectively, It's true that those regions have more "pro-russian" inhabitants than other parts of Ukraine, but around the time they broke away, thousands of pro-Ukrainains fled. (Crimeal which only voted 57-ish for independence in 1991 in contrast to other regions 85-95%) also has been settled with 500,000 to 800,00 Russians since that was annexed).
"So if the UN imposed free and fair elections, what happens if these areas choose to side with Russia? Do you think Zelenskyy would accept that? Wouldn’t Russia be then in a position to demand UN-overseen elections in all Ukrainian territories? "
The problem which immediately kicks any of this nonsense of Musks into touch is that the Russians wouldn't accept it because they know fine well that any sort of free elections would be lost.
But the only reason anyone is talking about this is because in desperation putin decided to call pretend referendums in areas he is trying to ethnically cleanse, areas which are war zones, where at least half the population has fled. And areas by the way which the kremlin has admitted does not know the borders of!
The whole thing is daft beyond belief.
Elon Musk is a man of many talents, and has provided great help to Ukraine with his Starlink mobile internet. He should stick to what he's good at.