Clear Baltic of German fleet, then send UK+US troops to Norway, when possible advancing them to Karelia, Eastern Europe then Germany itself ! It can be slow but it's certain
. If possible, take Norway with US (or put a British "shield" before it in Karelia) to build a factory and add to the ship logistics.
Raid West Europe if weak enough, and don't skip any reasonable opportunity for direct landings (UK sacrifice+US) on Germany if not strong enough. Even if wiped by counterattacks, the income shock (German cannot build next turn, US builds more) can be hugely helpful !
All this, while helping Russia survive against Japan. Just make your certain take of Berlin earlier
than his/her certain take of Moscow
Care for economics helps this in the longer run.