It’s the other way around. Russia can’t win the war in Ukraine any more, the best they can hope for is not to lose.
The success of Russian army has been … suboptimal
Ukrainians have already demonstrated their army is better trained, organized and motivated than the Russian army. They captured the imagination of billions around the world and are recieving aid worthy of that support. While this war lasts Ukraine can sustain the war almost indefinitely, certainly for several years.
In the meantime, Russia is on the brink of defaulting on their debts, their economy is tanking and the Russian military is scrambling to bring more combat troops to Ukraine.
The thing is, most Russian combat troops already are in Ukraine, they’re now bringing in reinforcements from the far east and mercenaries from the south to compensate. Ukraine can sustain the war for years, Russia has no more than a few months of a fight left.
The most Russia can hope for now is not to win – present terms to Ukraine the latter can accept (no NATO or foreign bases, but Russia has to offer concessions as well) or else resort to weapons of mass destruction, destroy Ukraine and make themselves a pariah state worse than North Korea. These are the two ways Russia can manage not to lose, but neither can be constructed as a “win” either.