Zeros only had P-39s for lunch above 10,000 ft. Unfortunately, most of the combat (high alt Betty raids with Zero escort on Port Moresby or Guadalcanal) was well above 10,000 feet.
Below that it was far more even.
And as long as the P-40s had competent pilots, as is true of Wildcats, Zeros did not have them for lunch. The P-40 has many exploitable advantages over the Zero that can be made use of in combat.
The overwhelming factor in Japanese air success from Dec. 41 through 42, when they had it, was superior pilot skill, not the Zero.
Had the Dutch and British Brewster Buffalo pilots had the same experience and level of training as the IJN/IJA pilots in the early war, I suspect they may have been able to keep the relative kill ratios fairly close.
