Since Russia is gradually taking over Ukraine in the war, the answer is simple. And it should be done whether or not Zelensky decides to set up elections. Russia should set up Ukrainian elections in the land that they took from Ukraine (the Donbas, etc.). And then invite all Ukrainians to come there to vote, including the ones that fled Ukraine at and before the beginning of the war. Since Russia will win the war anyway, and since Russia has stated that they don't want Ukraine (outside of what they have already taken), this will simply set things up for when the fighting is finished. I mean, since Russia doesn't accept Zelensky as anything other than a terrorist, why not legitimize Ukraine for the Ukrainian people, right now?