Complex sentence: He was also a mail-order salesman, polygraph examiner, sheriff's deputy, an insurance agent, owned a pharmaceutical company, and operated a public relations firm, of which his clients included the Phelps Dodge Corporation and the Salt River Project.
Split into simpler sentences: He was also a mail-order salesman, polygraph examiner, sheriff's deputy, an insurance agent, and owned a pharmaceutical company. His public relations firm had as its principal clients the Phelps Dodge Corporation and the Salt River Project.