What he likely means "ending the war by diplomatic means" is not talking or negotiating with Russia. No, that would be worst heresy imaginable. When he has previously talked about the use of diplomacy to find peace, what he really means is for Ukraine redouble it's efforts to beg for more money and weapons, but also get US and Europe to put more pressure on countries like China and India to ditch Putin and support Ukraine instead. Zelensky has talked along these lines before. Make his position seem reasonable to those who who want Ukraine to seek settlement, when it really isn't any different from "Zelensky's peace plan" that can be summed up in demand Russia's unconditional surrender as a precondition to any kind of dialogue.

I fear it's this kinda crazy talk that we are looking at. Zelensky or his inner circle just bring themselves to talk to the Russians, nor can they talk about things like giving up even places like Crimea. They just can't give an inch and we all know what happens to the reeds that don't bend with wind.