Even Zelensky's number one opponent, Poroshenko is against holding wartime elections.
Simple answer is that during wartime elections, Zelensky will probably win another 5 year term as people generally "rally around the flag" during wartime. Opponents want the elections after the war, feeling they have a better chance of wining. Good example of a similar situation is Winston Churchill, who lost elections after the war.
Ukrainian opposition leaders dismiss idea of wartime election Mar 6, 2025
https://www.reuters.com/world/europe/ukrainian-opposition-leaders-dismiss-idea-wartime-election-2025-03-06/
Zelensky agreed to hold elections during the most recent negotiations with the U.S. That’s why Putin was making the crazy eyes and babbling nonsense in Murmansk about UN takeover of Ukraine and BRICS joining the ceasefire talks last week.