The only reason General Zaluzhnyi could justifiably be removed is his failed counteroffensive. However, there's likely no other military leader in the country who could have done a better job, and his military qualities far outweigh the negative, petty differences he has with Zelenskyy. Ukraine has developed an incredibly successful defensive position— one that has remained strong due to Zaluzhnyi's ability to boost soldier's morale and continue to train new soldiers. Firing him would have no positive outcomes, but it could have negative ones.
First and foremost, President Zelenskyy has made no decision yet regarding Zaluzhnyi's future in the military. However, there are multiple reasons for Zelenskyy to consider dismissing him, including his creation of a charitable foundation in 2022 — which has been seen as the potential beginning of a political party to challenge the president. It's true that the majority of Ukrainians are against firing Zaluzhnyi, which is why Zelenskyy has taken a cautious approach.