Actually I think Funked has a point.
I have record of the test between the A6M2 Zero and the P-39D, P-51A, P-38F, P40F, F4F and F4U-1(early) in late 1942.
The P-39 was able to outclimb the Zero to 10,000FT. This may not seem like much but when you consider that same Zero outclimbed the P-38F, P-51A, P-40F and F4F to 10,000FT it is somewhat impressive. For the record the Zero and the F4U were very close with the F4U having the advantage between sea level to 5,000ft and almost even 5K to 19K with the Zero having a "slighty higher average rate of climb".
That's a little better.