The thing is what does peace with UK and its allies mean. are we talking about a Germany that has beaten Poland, France, Norway, lowlands etc but for some reason isn't fighting the UK. Or a Germany that avoid all that and is only fighting Russia?
The problem with the first is I can't see how GB and it allies stay out, and I can't see how Germany can beat them on this schedule (or in fact at all)
The second is better for Germany obviously but there's still the question of Poland between them. I think the single best scenario for Germany is for some reason the USSR in say 1940 invades Poland, the Red army is not ready for this and struggles* and Germany seizes it opportunity to invade through Poland and on into Russia. downside to this is Russia is mobilising already, but an upside is Germany might actually find itself with international favour** and Russia with none. The big problem here is after the Finnish debacle, the soviets are going to need a really good reason to initiate an invasion of Poland (as opposed to just taking the opportunity presented by the German invasion of Poland). So Maybe a diversion point is the soviets don't invade Finland but instead Poland? But if there's no prior Finnish invasion the weakness of the red army is less known.
Either way Germany vs. USSR only. It's going to come down to Germany timing it just right so that it's amassed enough logistics and resources (none of the 3 months worth only bollocks) before the Soviets sort their army out. Problem is doing that without invading somewhere earlier first is going to put a massive strain on German industry and in the scenario above they would be doing this just on the off chance the Soviets just happen to invade Poland***. No invasion of France/west means less men and material losses but also less combat experience with a tactic they're going to need to be perfect at for Russia. Ultimately I think it's possible for Germany to get to Moscow and either take it out of commission or to actually take it. Especially if we add some change in the weather maybe the Sep/Oct rain holds off a bit that year. They're are going to need oil from somewhere though. Ultimately though I don't think this beats Russia, entirely, but if Russia is alone in the world they might struggle to fight back past that in a mass military organised way as per OTL and instead it turns into Germany trying to hold a massive amount of land while the Soviets do their best to make it as hard as possible from east of the Urals. Maybe Japan seeing the soviets humbled now decide they can risk taking an opportunity north and not south at this point? (although fighting wars in two massive countries, not a great idea), this has the knock on effect of not riling the US and colonial powers up.
One thing though Nazis are gonna Nazi, they will start containing and then liquidating the local population etc. Maybe they can keep that quiet from the international community, maybe the international community will be more tolerant of it since there's no western European invasion and it will be happening in Russia, more willing to accept German mitigation "those rehousing facilitates outside Kiev really are nicely painted after all". Either way it will effect international impression at least somewhat and it will certainly increase local resistance.
*OTL they didn't exactly impress anyone even when Germany had gone first from the other direction,
**if the soviets did do this it actually feeds into Hitlers "Bolshevik threat", and even if the the rest of the world don't suddenly jump on side with him, they might be happy to see him and Stalin fight (especially after the international surprise of the M-R pact)
***maybe the M-R pact is a bit more friendly and Russia lest slip to Germany that it's going to invade Poland, or maybe the pact gives an opportunity for a better then OTL German intelligence (and worse Russian counter intelligence) and the Germans find out through espionage?