Zimmerman worked as news editor of the Sedro Woolley Courier-Times and as editor-publisher of the Cowlitz County Advocate in Castle Rock before buying the Camas Washougal Post-Record in 1957 and publishing the paper for the next 23 years. The Post-Record won first place in the nation in 1960 for community involvement and won many awards for news, editorials, advertising, and community service. He also served as President of the Washington Newspaper Publishers Association. Among the many leadership roles he had were serving as President of the Lions Club and a Chamber of Commerce officer in Castle Rock and President of the Kiwanis Club and Chamber of Commerce in Camas. For his many years of community service, he was named as the “Citizen of the Century” for Camas. He served 22 years in the Washington State Legislature, had leadership roles in both the House and the Senate such as serving as Chairman of Legislative Budget Committee in 1987 and sponsored key pieces of legislation, such as the state’s first Solid Waste Act in 1969 and its first tough oil spill bill in 1970. He resigned from the State Senate in 1988 when Governor Booth Gardner appointed him to the state’s Pollution Control Hearings Board. As one of the three full-time hearings board members in Environmental Hearings Office, he heard appeals on air and water pollution, shorelines appeals and helped coordinate officers of two other appeals boards.