Michael Mugaku Zimmerman Roshi was born in Chicago, Illinois, in 1943. As a teenager he moved to Arizona where he finished high school and began college. Moving to Utah, he graduated from the University of Utah and then attended its law school. Following graduation he moved to Washington, D.C., for a judicial clerkship, and then to Los Angeles where he worked for a large law firm until 1976 when he returned to Utah to teach law briefly.
He served as part-time special counsel to Utah’s Governor, had a litigation law practice, and served as a Justice and then Chief Justice of the Utah Supreme Court. In 2000 he returned to law practice as a partner in a multistate firm. In 2011 he started Utah's first appellate boutique, the law firm of Zimmerman Booher, and continues in the active practice of law.
Mugaku Roshi came to Zen relatively late. He first ventured into meditation in 1993 as a way to find some grounding during his first wife's year long struggle with terminal cancer. Shortly thereafter he met Diane Hamilton, now Musho Roshi, then a coworker in the Utah courts. At her suggestion he attended an introductory class at Kanzeon Zen Center in early 1997.
Soon afterward he began to study with Genpo Merzel Roshi. He and Diane were married by Genpo Roshi in 1998, the year he received Jukai. They received Shukke Tokudo and became monks together in 2003. They were joint Shushos during the Spring Ango in 2005, and received Denkai in early 2006. He received Dharma Transmission in December 2006, seven months after Diane. In 2018 Michael received the final seal of Inka from Sidney Musai Walter Roshi, a successor of Genpo Merzel Roshi.
Mugaku Roshi is a nationally recognized teacher of mediation and mindfulness for the legal profession. He and Musho Roshi have presented programs for the Utah State Bar and other legal organizations.
Together, Diane and Michael have four children and five grandchildren.