This question resolves to yes if Putin is no longer president of Russia while Zelensky is still president of Ukraine.

For the purposes of this question, the reason for either president to no longer be president is irrelevant: lost election, death, destitution, coup d'état, anything counts. If Putin becomes prime minister while someone else assumes the presidency, Putin will no longer be considered president, even if there is broad agreement that the official president is no more than a figurehead. Ditto for Zelensky.

For the purposes of this question, in the event that either president would lose de facto control over the capital of his country, he would no longer be considered president, regardless of the de jure situation, even if he retreats to some other place and maintains a government in exile of any sort. It's a bit arbitrary, but I think it makes things easier to resolve, as consitutional issues of this type can become very tricky to resolve objectively.

The question resolves as soon as either man is no longer president. If for some reason it happens at exactly the same time for both of them, it resolves as N/A.