Thank you, Vance. What I’ve found since I posted is the importance of Italy in support - as you mentioned. Italy takes a territory, Germany reinforces. Repeat, over and over. This gives Italy IPCs, preserves whatever leftover Italians made it through the battle, allows Germany to not be attrited, and allows German air power to land and lock down territories.
In my last game, I forced a retreat from Moscow with a combined German force of approximately 36 Infantry, 10 Artillery, 6 Mech Infantry, and 14 Armor… along with typical Luftwaffe presence - Tac bombers shifted to East Front to combine with Armor, Fighters playing defense in Italy/Germany. I was able to sustain German Infantry by having Italy do the heavy lifting.
It is a very methodical and patient process - Russia remains strong until Turns 10-12, but eventually has to give ground.
The important part is strong Atlantic and Med play, to allow you the time it takes to wear down Russia. This is not a quick kill strategy.
I like the 3 Armor/3 Infantry suggestion!