Complex sentence: Frederic C. Hamilton founded Hamilton Oil Corporation in the late 1960s, built it into an international oil company and also formed a domestic gas company, both of which he merged into a major integrated oil company in the mid- 1980s.
Split into simpler sentences: Frederic C. Hamilton founded Hamilton Oil Corporation in the late 1960s. He built it into an international oil company and also formed a domestic gas company, both of which he merged into a major integrated oil company in the mid- 1980s.