That was a generalisation, but what Im saying is that version to version, for both a/c, the Ki-43 is usually the slower, I leave it to you to look up all the #s.
Its true that the later Ki-43-II was a tad faster than the earliest Zero (A6M2).
Its main opposition was the P-40E, P39D, and P-38F, and F4F over New Guinea, and the Solomons. In China it fought right up untill the end against the USAAF and the RAF although by wars end it was hopelessly outclassed by faster allied types.
Interesting side note, The AVG "Flying Tigers" are oft quoted as fighting "Zeros" over China. Truth was they were fighting Ki-43s, but realised it only much later. China was left up to the IJAAF and the IJN had almost no presence in the CBI war.
Later