Born in Stralsund, Zegelmaker is of Curaçaoan ancestry and was ordained to the priesthood in Kiel on May 16 1973. On April 16, 1999, he was appointed Auxiliary Bishop of Kiel and Titular Bishop of Einthissen. Zegelmaker received his episcopal consecration on the following May 24 from Bishop Alfons Spielmeyer, with Bishops Hans Thomassen and Friedrich Mandel serving as co-consecrators.
He was named Archbishop of Schleswig-Holstein by Pope Sixtus VI on November 22, 2002; he was installed as such on January 21, 2003. This effectively made him Co-Prince of Elsevia, as the Archbishop of Schleswig-Holstein shares sovereignty of the country along with the President of Frisia.