Complex sentence: They become so successful that they take over Planet Express when it is discovered that the Professor was declared legally dead three years ago, the name of the company is then changed to the name of the boys delivery route,'Awesome Express'.
Split into simpler sentences: They become so successful that they take over Planet Express when it is discovered that the Professor was declared legally dead three years ago. The name of the company is then changed to the name of the boys'delivery route,' Awesome Express'.