Just out of curiosity, I've seen lots of information about the Zeke or Zero going up against the Allied aircraft. But would anyone have an idea of how they would do against the Messerschmitt Bf109E? For example if in an alternative universe the Flying Tigers were a German unit rather than American flying the Bf109 instead of the P40?
Basically use the same tactics of the P-40: boom and zoom, don't engage in a turning fight. If hit the Zero would die instantly. AFIAK the E-series Bf109 handled about the same as the P-40, so the same tactics would work. Now the Bf109F would be overkill. I think the same applies to the other Japanese army fighters, as the Ki-43, introduced in October 1941, is actually slower than the Hurricane Mk. II, which was slower than the Bf109E.
If the Luftwaffe sent a 'Condor Legion' to China, the Japanese would suffer quite badly at their hands, as unlike the AVG the Luftwaffe already had combat experience and modern tactics that would mince the IJA fighters.
I've discussed a Condor Legion for China in several forums including this one IIRC and generally speaking anything the Germans send in 1940-41 or later (assuming no WW2 and continued Sino-German alliance, no Japanese deal) would massacre the Japanese equivalent due to the better tactics and equipment the Germans had. They had developed a lot even just during the SCW, while the AVG had to develop their tactics when they got to China; of course the P-40E was a better aircraft, properly handled, than the IJA fighters and bombers they faced, so that really helped. The Americans pilots were also willing to learn and innovate, so they developed fast if they survived, so I'm thinking if the SCW Condor Legion vets form a nucleus for another intervention abroad, they'd bring enough combat skills and wariness of a new opponent (they learned the hard way in Spain vs. the Soviets) that they'd perform well right off the bat. Plus if it is in 1941 then the Bf109F is sent, which was a superlative fighter and bested the P-40E in North Africa and smashed the 1941 brand new Soviet fighters, so the 1941 standard and brand new IJA fighters would suffer badly if facing that.
If you send FW190s in late 1941 or 1942 then you'd be clubbing baby seals.