Many posts on different websites mention that Superman became stronger than Zod because he spent more time exposed to our yellow sun.
Is general Zod more powerful than Superman - Quora
However, this idea doesn't seem congruent to me with the idea that Superman will lose his powers when exposed to a red sun. If he can accumulate powers for years, why would his powers immediately vanish when exposed to a red sun? That makes me suppose that the idea that Superman became stronger than Zod isn't official, but a fan's explanation.
Is it canon that Superman became stronger than Zod because he spent more time exposed to our yellow sun?