My best in a Zero was 17 kills and all were with only cannon, I landed with 90% of my MG ammo, was almost outa gas. The 20mm Type 99 MK II it has is the second hardest hitting gun in the game bested only by the Hispano in the 20mm class, you nead to be much closer of course to hit consistently with it though, so it realy only takes a few hits to kill a plane with it. Those were all vulches, one or two air to air kills. Even in air to air mode I still can get 10 kill sorties without to much difficulity, the ammo is suficent for that without reloading.