I'm not sure that either side 'win' in the short term. My gut feel is that we'll enter a period of to and fro in the east of Ukraine, which may well last as long as Putin is in power. Ukraine won't quit, that's for sure.
The south I'm not so sure about, I think that might come down to logistics again - can Russia resupply quickly enough if Ukraine pushes back and defends in force?
How long Putin lasts maybe depends on how effective the sanctions are, and whether the Russian military leadership will tolerate endless ongoing losses of men and material.
I also don't see Russia trying to expand into anywhere else anytime soon. NATO and Finland in particular, are forewarned, and Russia's military is already overstretched and hurting. Opening another front would be absolute madness.
If Putin could just do the decent thing and die quickly, I think this could be resolved in reasonably short order.
All just mho, obviously, and depends very much on the west continuing to support Ukraine.