Depends on which date you use as the start of WW2. The A6M Zero did not begin ful production until 1940.
IMHO: Prior to Dec. 7, 1941, there were two regional conflicts going on. One centered in China and the other in Europe. After Dec. 7th, it all got bundled into one big "world War". So, the Zero was in service before them. Three aircraft made the whole trip!
Right you are! The last 137 A6Ms were delivered in August 1945. 52 from Nagoya Mitsubishi and 85 from Nakajima.
