Zundel commanded an artillery battalion on the Western Front during World War I, and was artillery officer of the Sixth United States Army in the Southwest Pacific Area during World War II, participating in many of the operations there. In May 1944 he became commander of the 41st Infantry Division Artillery, and was decorated for gallantry in the Battle of Biak and the Battle of Mindanao. After the war he became chief of the Counter Intelligence Corps and commandant of its Corps School. He served in the Korean War as Inspector General, Far East Command, and Inspector General, United Nations Command.