Zero Fighter by Akira Yoshimura
The factory in question was the Nogoya Aircraft Works. They built not just Zeros, either.
The oxcart trip from the Aircraft works to the airfield took 24 hours.
Every single plane built there made this trip by oxcart.
They increased production because they built more and more at other factories. Japan didn't have the resources to waste a valuable factory that was constrained by the speed of oxcarts.
The road was never improved, and the more planes they moved, the worse the road got. Part of the reason for the oxcarts was the size of the streets, part was that they vibrated the airframes less, apparently. The oxen were by mid 1942 trucked back closer to the factory to let them rest (the trip was 48 km to the airfield). They started with 50 oxen, by 1944, they were dying of exhaustion and they had only 30.
LOL. Oxen.
BTW, I'd use more complex formatting (don't EVEN get me started on that
), but bold on this forum doesn't look good to my eye in most cases, and I think it is less legible. I liberally use italics as it is.