How good was the Zero at durability in tropical conditions?
I believe the Spitfire in particular suffered in the tropics, and that in the Pacific air war a big advantage American planes had was that they were better able to tolerate the conditions. This is partially because of the American habit of making rather heavy airplanes and then giving them heavy engines for sheer brute power--a practice Americans could afford because they were in the period a major exporter of petroleum and could also afford the logistics of big fuel shipments. Also US oil wells, particularly the Southern California ones, yielded inherently high octane oil that could easily be enhanced to high levels, over 100, so American designers (and their British allies) could rely on such fuels and thus design engines for higher compression ratios.
But I think the real key factor was the domestic (plus colonial) geography and politics of the USA. The US spans a wide range of climate zones, and with key colonial possessions which tended not to be relegated second-string machines because of their cruciallness--Panama Canal Zone in particular, but Hawaii was also quite important and the major purpose of conquering the Philippines was to provide a major naval and later air forces base--being tropical, the US air forces, Army, Navy and Marines would be deployed in conditions ranging from Arctic (Alaska obviously, but huge swathes of the continental states suffer conditions not much different from Arctic in winter!) through arid desert to fully tropical (and again, while places like Florida are not technically tropical, they come darn close in mid-summer, so again the ultra-extremes of distant colonial possessions are nearly rivaled by CONUS conditions). Politics enhances military considerations; the democratic nature of Congress means that military funding tends to get spread out among all the states so basing, rationalized sometimes very dubiously by military scenarios, is all across the states.
So when the Army or Navy procured an airplane off the production lines, even in peacetime they knew one plane might be based in Arizona, its next neighbor on the line sent to Florida or Panama, another to Maine or Alaska. The same design then had to operate in any of these climate zones, and the aircrews and maintenance teams had decades of experience dealing with the maintenance and operational challenges all of these conditions posed. In fact not just different planes from one production line (which might conceivably be modified for their specialized environments) but the same airplane might have to cycle through all of these diverse bases, as the military tends to have exercises and contests that bring together planes from bases all across the nation.
Making a plane that can operate one week in Maine in mid-winter, and the next summer in Panama or Arizona, and the whole aeronautical industry having grown up with that challenge before it from the beginning, puts a premium on generically rugged design, which helps explain the American preference for rather heavy planes with very heavy power plants.
Contrast that to the Germans, who had just European climate zones to consider normally.
Britain and Japan are sort of intermediate cases--both are like Germany set in one limited range of climates, but the British of course had a colonial empire all over the world, with even more diversity than the Americans to deal with. Politically though those colonial possessions didn't have the clout in London even a small and peripheral American state has in Washington; strategically, the British saw their front-line military challenges in Europe itself whereas colonial warfare was ideally done on the cheap with limited forces. So even British designers, almost as much as German ones, were preoccupied with European climate conditions, whereas colonial forces typically got hand-me-down previous-generation, obsolete aircraft, originally designed for European combat and modified on a catch-as-catch can basis by underfunded (if experienced!) local maintenance crews.
So it was that OTL, it was mostly American airframes on the Allied side in the Pacific, with the local Australian designed-and-produced Boomerang being at least as important as any Spitfires the mother country could spare, which rapidly deteriorated in the tropical war zone.
Japan's war, before they escalated it to global proportions, was in China. A lot of China has conditions more like the USA than Europe--cold winters and fairly warm to perhaps hot summers in the north, very warm subtropical conditions in the south. So even if Japanese designs did suffer from some of the myopia of European ones, in combat and on station the local forces would soon learn about their limits and how to overcome them, and their experience would affect the orders their respective high commands placed with Japanese aero firms.
I'm guessing that despite being lightweight, the Zero was reasonably well tropicalized, with an initial eye on the challenges of operations in southern China as well as a speculative one on Indochina and points south and west of there.
The criticisms that focus on the folly of attempting to buy weapons from the same guys you expect you might have to fight soon, and the unlikelihood that those soon-to-be-foes will offer to sell their best stuff, are well-taken. As are the ones that point out that the Zero was a dead end.
But, given a flying corps like the Japanese carrier pilots, encouraged to think of a strong and bold offense as the best defense and to be fatalistic about their certain doom should an enemy's guns find their target, it was a very respectable weapon indeed for its day. It's all very well to say later planes would be better, but the Aussies needed planes today. A Spitfire might wipe the skies of Zeros--until it corroded, or its fuel lines rotted, in the tropical heat and humidity, or it choked on the dust that somehow shrouded the wet landing fields.
The Australians weren't going to get Zeros. If they had them though one shouldn't sneer at them.