I don’t know.
There are legitimate doubts about that election that have not been properly investigated. The Democrats and the US establishment have subsequently behaved abominably. If you do not recognize that election as legitimate I would not complain about your opinion.
But this point is not about a US election.
Zelensky was not elected in a close election. It was in two rounds, in the first he was #1, with a 2X plurality (30% of the vote vs Poroshenkos 15%), in a field of 30+ candidates, and then he won the second round in a landslide. No quibbles on that one. Zelensky is much more legitimate than Biden.
He’s also a lot more legitimate than is Putin.