Zirnkilton, a Republican, served for eight years (four terms) in the Maine House of Representatives from 1982 to 1988 and again from 1992 to 1994. He represented part of Hancock County, Maine, including his residence in the village of Seal Harbor in the town Mount Desert. During his final term in the House of Representatives, Zirnkilton served in leadership as Assistant Minority Leader. In 1994, when then Congresswoman Olympia Snowe decided not to seek re-election to the U.S. House of Representatives for Maine's 2nd congressional district, Zirnkilton sought to replace her. Zirnkilton lost the primary to fellow State Representative Richard A. Bennett, who eventually lost the general election to State Senator John Baldacci.
Zirnkilton is known for providing the opening narration of all US shows in the Law & Order franchise. He received the job after he was originally hired by series creator Dick Wolf for a small part on Law & Order. Zirnkilton has also provided voices for Family Guy and The Rugrats Movie. He was a narrator for Faith Rewarded: The Historic Season of the 2004 Boston Red Sox. Zirnkilton narrated Ruby Ridge: Anatomy of a Tragedy on Investigation Discovery. He also provided the voice-over for a Sky One advertisement for the channel's Law & Order airings. Zirnkilton was the narrator for TLC's Code Blue: New Orleans and the syndicated series Arrest & Trial. He has been the announcer for the Kennedy Center Honors, and for the past thirteen years he has been the onstage announcer for the Top Cops Awards in Washington, D.C.. Zirnkilton's agent is william Morris Endeavor.
Zirnkilton also provides voice overs for political ads, notably during Susan Collins re-election campaign in 2014.
