My guess would be if Ukraine does surrender then Russia will insist that it becomes effectively demilitarized and breaks relations with the west.

That would mean the end for the Banderites and the Nazis, no matter what form the unconditional surrender takes. Which is interesting in itself, since Zal is a Banderite fascist, one among many in the state apparatus. My bet is Russia will not tolerate these people in any way, shape or form, thus if the Ukrainian state survives (as a rump state, without Kharkov, Nikolaev and Odessa perhaps, but we'll see) - the entire government would have to be purged. If they coup Zelensky and surrender, they will have to go as well, I think