Complex sentence: When Miller went bankrupt in 1933, Offenhauser and another Miller employee, Leo Goossen, bought the shop and the rights to the engine, which they further developed into the Offenhauser engine.
Split into simpler sentences: When Miller went bankrupt in 1933, Offenhauser bought the shop and the rights to the engine. He and another Miller employee, Leo Goossen further developed the Miller into the Offenhauser engine.