Yes, on G2, buy 10 artillery in Germany (cheap strong attack power when combined with Infantry). Attack Baltic States and Estern Poland I3.
On G2, move West Germans AA guns to Germany
On G3, mov artillery + 6 AA guns to Poland
On G4, reinforce Baltic States with the 10 artillery, 6 AA guns, the infantries/artillery/mech units from the original setup (should be 16+ infantry, + a good 3 other artillery) + German air force planes. No need to declare war, collect 5 IPC one last time.
The Russian player will need to abandon Leningrad because of the considerable offensive power of these units (and won’t be able to counterattack because planes will be helping the defence).
A Medium Italian force (constantly reinforced) should be able to clear the path every single turn for this stack to advance (supported as appropriate by follow through mechanized units). If the russians leave a sustantial stack to block this, the italians pass on and the Germans go kill russians with their robust airforce (even better if the Germans have a big enough stack to risk it and go on their own without the airforce).