In the 1960s and 1970s, Zumach was a member of the Bergisch Gladbach town council and chairwoman of the school and culture committee, in addition to her diverse involvement in the Evangelical Church. In this position, she initiated the naming of "Nikolaus Cusanus" for the grammar school on Reuterstrasse and "Dietrich Bonhoeffer" for the girls' gymnasium in Bensberg.
Zumach was active in the Evangelical Church since the 1940s—locally, in the Rhineland, in the EKD and in the global ecumenical movement.
From 1972-1992, Zumach was the general secretary of Protestant women's work in Germany. In this role, in solidarity with the black women of South Africa, she initiated the boycott of fruits and gold coins from South Africa in 1978. This action, which was continued until 1992 and which was joined by numerous parishes and synods, was initially rejected by the EKD Council. But after apartheid was overcome in 1994, the highest body of the EKD revised its position.
As early as 1946, during her church music studies at the Cologne University of Music, Zumach was involved in the Protestant student community. Afterwards she was on the board of the Protestant Academic Union in Germany until 1968.
In the 1970s, 1980s and 1990s Zumach was part of the EKD's six-member delegation to the central committee of the World Council of Churches (WCC) and participated in WCC assemblies in Nairobi (1975), Vancouver (1983) and Canberra (1991). In 1979 she was one of the co-founders of the “Plea for an Ecumenical Future,” which is committed to the “Conciliar Process for Peace, Justice and the Integrity of Creation” founded in Vancouver.
Her ecumenical commitment also included the founding (together with the Catholic Women's Association) of the German Committee for the World Day of Prayer for Women in the early 1970s, of which Zumach was chairman until 1982.
Even after her retirement and resignation as general secretary of Evangelical Women's Work in 1992, Zumach remained active: until 1996 as chairwoman of the Action Community Service for Peace, the umbrella organization of 34 Christian peace, development and human rights groups, and until 1995 as chairwoman of the Bavarian Mothers Service/FrauenwerkStein in the Evangelical Lutheran Church of Bavaria.
Zumach was born on 12 September 1926 in Dörscheid am Rhein and grew up in Ems an der Lahn, where her father was pastor and dean of the Evangelical Church in Hesse and Nassau. She leaves three children and two grandchildren.