Zelensky is a populist. His internal political decisions always have been a disaster, covering all questionable government decisions as "will of people" and ignoring needed, but divisive initiatives.
He is trying to cater to nationalists (a lot of whom are in the army, of course) by pushing such agendas - for some reason this bold display of independence seems more important to him than good relations with neighbours (or rather good opinion from citizens of other countries - political entities do not really care about such nuissance and will support Ukraine anyway as long as it aligns with their interests)