Generally they help eachother quite alot.
Since im the only one here (it seems) that think going after Japan is crusial to victory.
Manly Germany sits back and holds as long as possible, making a attack on West russia/Cauccasus When Japan have amased a lot of forces to make Russia withdraw back to moscow.
They take Cauccasus togheter.
Japan goes after Africa, witch usually is a bit “softer” after the German initial attack.
Japanesse fleet is in atlantic on Round 3-4 half going round southamerica taking Newzeeland and brazil other half goes round Southafrica taking everything as it passes.
Figs can be sent to Europe if Germany are getting whacked.