The Zero fighter wasn't "countered" as if it was so unique that it was unbeatable until it was suddenly rendered hopeless. The Allies began the war relatively unfamiliar with it, then gradually learned its strengths and weaknesses through combat experience and evaluations.

That is an identical learning process to any nation viewing an aircraft of an opposing nation in war. The Zero was not so uniquely flawed that it was obsolete the moment its "secrets" were revealed. It had strengths and weaknesses. Like all aircraft, including its opponents.

The Allies sought to maximize their aircraft's strengths and minimize their weaknesses while exploiting the weaknesses of the Zero. The Japanese did the exact same thing in reverse. The British did that to the Germans. The Germans did that to the Soviets. The... you get the point

This didn't end the air war in an afternoon after an Akutan Zero flight test. Nor did it suddenly become a one-sided contest. The Japanese put up vicious, and effective, air resistance against the western Allies into 1944. Almost like an entire air war wasn't decided by tech.

Japanese conventional air power began to fall apart in 1944, for reasons that honestly had little to do with the strengths or weaknesses of a single fighter type. The Japanese had held their own for over half the war. As Nicholas Millman points out:

The lack of protection on most Zeros was a noteworthy weakness, but one that also fostered strengths. It is the same as the very poor rate of climb on the F4F-4. A weakness, but not one that rendered the plane hopeless. Again, all aircraft have these strengths and weaknesses.