@Ghostse You got the wrong fighter as the Hellcat like the F4U Corsair was outright better than the Zero. Only at the time current US Navy fighter the Zero was better than was the Brewster Buffalo. And even it could out fight the Zeros once USN pilots stopped trying to dogfight to the Japanese strengths and adopted the Thatch Weave amongst other tactics.
You are correct on the 25mm, too many diameters getting tossed around. fix'd.
The Hellcat still had issues with Zeroes until tactics & training improved, which they did. (And the Corsair was better once they got bugs worked out )
As did the number of fighters. The Thatcher Weave was incredibly effective, but it was basically a 4 on 1 (or two on one) tactic. Which even out numbered you could get away with due the US planes' ability to soak damage, and the Zeros ability to turn into a fireball with one good burst.
(The weave was also easy to counter if the Japanese pilots could recognize it and adapt - but given combat losses, only very good or very lucky Japanese pilots were about to experience and survive to be able to recognize it the next time. and again, that's where crew survivability comes in)
Anyway, comes down to the same point: US pilots had better odds of surviving even a losing dogfight and had the opportunity learn and to get better, Japanese pilots tended to not survive their loss.
Even if we take Russias most optimistic casualty claims for the Ukrainian Army they are nowhere near running out of military aged males. The casualty rate in this war is unprecedented for modern times but when compared to even a single World War Battle like Ypres or Verdun, it's an ant hill compared to a mountain.
I did a break down in Articles thread that Ukraine would take like 30 years before they reach the level of 1945 Germany, and that's when you count the "Casualty" numbers as deaths, round up, and figure a population drop of 25% for refugees/donbros, and ignore births.
Granted no one wants to be 1945 Germany, but its a long time out before they start needing to go recruiting in the prisons.