Complex sentence: Prior to his writing career, Leo was a successful engineer, owner and operator of Sterling Manufacturing and Design, located in Utica, Michigan, which (among other things) designed pneumatic and hydraulic systems for Chrysler.
Split into simpler sentences: Prior to his writing career, Leo was a successful engineer. He owned and operated Sterling Manufacturing and Design, located in Utica, Michigan, which (among other things) designed pneumatic and hydraulic systems for Chrysler.