From reading Shattered Sword, IIRC, it took a lot of time to get from low to high altitude. Pretty much had to choose one or the other early on their patrol?
Correct - if you were at low altitude, you often couldn’t climb back to altitude in time to do anything significant, let alone intercept incoming enemy aircraft.
To give you some idea, the Zero’s time to altitude was a bit over seven minutes to go from near sea level to 19,685 feet. Their initial climb rate was about 3,340 feet per minute. Keep in mind that their climb rate slowed greatly as they gained altitude, like all prop planes. The Zero climbs like some early jets, but even that was not enough to get it from splashing torpedo bombers on the deck to intercepting a Dauntless at altitude before the latter could begin its dive in any amount of time to be useful. This was a fact of life of air combat until the second generation jets like the F-86 started showing up with their 7000+ fpm climb rates.