A popular legend stated that the F6F was designed specifically to fight the Zero. Preliminary design work on the Hellcat actually began as early as February, 1938 and was an attempt to upgrade the performance of the Wildcat to bring it up to the level of designs emerging in Europe.
The FM-2, on the other hand, WAS designed to give the Navy a version of the Wildcat with performance closer to that of the Zero. Five hundred pounds was stripped from the airframe and the engine. With 150 extra horsepower the little FM-2's performance now exceeded that of the Zero 52's at low level. Performance varied at different altitudes, in both speed and rate of climb. Rate of roll was identical at speeds of 184mph and under, but the FM-2 was superior at higher speeds. Turns were very similar, with a slight advantage in favor of the Zero 52. The Zero could gain one turn in eight at 10,000 ft. (Technical Air Intelligence flight test data gathered from comparisons with captured Zero 52 at NAS Patuxent River, July 1944.)
Regards, Shuckins