Complex sentence: Persistence by the brothers eventually led to their request being granted in May 1975, and managed to negotiate a deal with the corporation by selling New Zealand cheese to the US to offset the high costs of importing plant equipment.
Split into simpler sentences: Persistence by the brothers eventually led to their request being granted in May 1975. They managed to negotiate a deal with the corporation by selling New Zealand cheese to the US to offset the high costs of importing plant equipment.