if Putin is still Russian President. So, Zelensky is the only one who can negotiate now. So, it is impossible to have another one to replace Zelensky for negotiation.
Election is the only way to go to replace Zelensky. His chance to get reelected is poor. Ukraine constitution doesn't say you can't have president election during war. Zelensky cancellation of presidential election has legal issue. Ukraine should hold presidential election as soon as possible.