In my alternative universe, development of the Boomerang began in 1939, when Australia and Zealandia started to consider the chance of losing the supply of military resources from Great Britain in the advent of a World War conflict that seemed an increasing possible. In February 1940, the design process was spread up greatly and Australia was tasked with producing the main type, a ground attack focused version that is the IRL Boomerang. Zealandia was tasked with creating a higher performance fighter type, using Merlin engines that were first starting to arrive with Hurricane Mk.1s. By july 1941, the radial engined Boomerang prototype was flying and the type would begin to enter service by the end of the year. The Merlin version took a longer, first because it was impossible to get Great Britain to supply any, so production facilities had to be produced from scratch. Then, the type was almost canceled when the prototype, which first flew in October 1941, couldn't even match the speed of the radial engined Boomerang. However, the type caught a break when Zealandia was able to get Merlin 2 production facilities going, though half of the engines had to be shipped back to great Britain to supply the war effort there. This new version the ZAC ZA-12B was able to achieve 315 mph at 15,500 feet, a small but noticeable upgrade over the the radial engined version. Climb rate was increased to just over 3,000ft/m, and range was only slightly reduced. By January 1942 35 machines had been produced and were beginning in service trials. They were soon intercepting Japanese bombers attacking New Guinea, Australia, and Zealandia. achieving favorable success in these dire times especially compared to the ineffective Buffalo, but being less successful against escorting fighters than the Hurricane, whose pilots better new their plane's strengths and weaknesses. In July 1942, the G version entered service, equipped with a 1,350 hp Merlin 3, whose production was still limited by requirements to supply the European and African theaters. This version saw maximum speed increased to 330 mph, while armament was changed from four .303 machine guns to four .50 machine guns. 115 of this type were produced serving as the main fighter of the Zealandia Air Force, and a large part of the Australian Air Force until P-40s started to replace them extensively in mid-late 1943 (they almost exclusively served as ground attack planes along with their Australian brethren, or as interceptors for home defense with the B version). The final main version, the R, first flew in August 1942, the prototype simply being a G with a tropicalized Merlin 3 and 2 20mm Hispano Cannon added to the Bs four .30 machine guns. The production version, however, used a tropicalized Merlin XX, with productions restrictions eliminated now the United State's full production capacity was being realized. This put the airframe to its limit, and the tail was re designed as a result. The fuselage and cockpit area were also cut down to minimize weight for this new heavier engine, and optimize performance. 17 were built with just 2x 20 mm Hispano cannon, 25 with four .50 machine guns, and 21 with two of each before the availability of better aircraft ended production. This super Boomerang entered service in January 1943, and had a speed of 355 mph, with a climb rate of 3,100 ft/min and a range back to the originals 900 mph with the addition of new self sealing fuel tanks in the wing, first introduced mid way through the G versions production, and because of the weight reductions. This type, while relegated to mostly ground attack, achieved a 2.5:1 K:D ratio, due to as much to its dog fighting abilities, to the pilots better training and tactics by this point in the war. The last would be retired in July, 1945, as a new Commonwealth fighter, the Kangaroo entered service.