A6M1 - prototype
A6M2 - two versions (-11) and (-21), which had folding wing tips for carrier operations.
A6M3 - two versions (-32) with more engine output and squared wingtips for better dive and roll but shorter range, and (-22) with the older wing (better range) still with more powerful engine.
A6M4 - Turbo supercharger for better high altitude performance, but development was problematic and abandoned.
A6M5 - three versions (-52a), (52-b) and (-52c), each one having more protection and armament, including CO2 fire extinguishers in the wing fuel tanks, and behind the cockpit.:
52a - individual exhaust for greater speed. Improved 20 mm cannon with more rounds per gun. Thicker wing skinning was installed to permit higher diving speeds.
52b - 7.7 mm machine gun in the right forward fuselage was replaced by a 13.2 mm gun. armored glass 45 mm (1.8 in) thick was fitted to the windscreen.
52c - Armament increased to 3 13.2mm machine guns (1 in the cowling and 1 in each wing) and 2 20 mm cannons. Four racks for rockets or small bombs were installed outboard of the 13 mm gun in each wing. A 55 mm (2.2 in) thick piece of armored glass was installed at the headrest and an 8 mm (0.31 in) thick plate of armor was installed behind the seat. Wing skin was thickened further to permit even higher diving speeds.
A5M5-S - To intercept B-29s and other night-flying aircraft, armed with one 20 mm Type 99 cannon behind the pilot, aimed upward, similar in intent to the Luftwaffe's Schräge Musik installation.
A6M6 - to use improved engine, featuring water-methanol engine boost and self-sealing fuel tanks in the wings. Due to the unreliability of the fuel injection system, testing continued but the end of war stopped further development.
A6M7 - designed to meet a requirement for a dedicated attack/dive bomber version that could operate from smaller aircraft carriers. It featured a reinforced vertical stabilizer, a special bomb rack, provision for two 350-litre drop tanks and fixed bomb/rocket swing stoppers on the underside of the wings. Hhad a similar armament layout to the A6M5c.
A6M8 - New powerplant (Mitsubishi Kinsei 62 (1,560 hp)). Extensively modified cowling and nose for the aircraft. Armament: two 13.2 mm machine guns and two 20 mm Type 99 cannons in the wings. In addition, two 150 l (40 US gal) drop tanks on either wing in order to permit the mounting of a 250 kg (550 lb) bomb on the underside of the fuselage. Two prototypes were completed in April 1945 but it did not enter production.
A6M2-K - Two seat trainer version based off the A6M2. Also used as a target tow.
A6M5-K - Two seat trainer version based off the A6M5.
A6M2-N - Nakajima-built floatplane fighter (based on the A6M2-11 with a slightly modified tail).
So counting all the major versions plus the sub types shows 16 versions, although 3 of those versions were not put into production.
As for a "new" Zero, that would be the A7M Reppu, superior to the Zero in every way. It was almost ready for production when the war ended. The story of why it took so long to develop is too much to go into here.
