Germany+the Soviets vs Italy+Britain+France? How does that mean the Allies lose???
Soviets invade the Middle East and dismantle the British empire, while supplying Germany will all the raw materials it needs to fight the war, no eastern front for Germany, French belligerence in the Balkans doesn't exactly make them popular in the neutral world, while the Soviets set their various communist parties internationally against the Allies more so than even IOTL, while with France and Italy pushing into the Balkans (with more than 3 divisions actually, the French talked about trying to get up to 100 divisions there at some point, so between Italy and France they might well get some 20 or more divisions into Yugoslavia, with or without Yugoslav consent) they move forces away from the decisive front in France, which Britain probably also has to strip forces from to prevent the Middle East from collapsing, which allows Germany to have an even easier time there. Basically multiple fatal diversions of manpower, which collapse the Allied positions on the continent and in the Middle East/Asia, while then the Soviets could send a large aerial expeditionary corps to operate against Britain when TTL's BoB play out and the Soviet Baltic Fleet comes out to threaten the UK. The Soviets did after all have a strategic bomber fleet:
https://en.wikipedia.org/wiki/Petlyakov_Pe-8
which if the Germans helped provide engines for them to alleviate the Soviet issues with theirs, the British would have a problem.