Marianne Zels owned a fashion boutique in Vienna from 1899 and was technical director from 1910 to 1926 of the fashion department of the Wiener Werkstätte at Neustiftgasse 32 in Vienna's 7th district. After a short period as workshop manager at G. und E. Spitzer she taught fashion from 1926 to March 1938 in Josef Wimmer-Wisgrill's class at the Kunstgewerbeschule (School of Applied Arts) on Stubenring. Her brother Otto H. Zels (born 1878) was an engineer in the automobile industry and lived in Nice. In April 1938 Zels and her brother contacted the Technisches Museum Wien with a view to donating books, archive items and prints from the estate of their father Louis Zels, who had died in 1921. The museum had the items collected a short time afterwards. Louis Zels, born in 1846, was director of the 1. Österreichische Canalschiffahrt-Gesellschaft and editor of the magazine Danubius (1885–1908); Marianne and Otto's mother was Charlotte Jellinek, daughter of the rabbi Adolf Jellinek. As a Jew, Marianne Zels was forced by the Ministry of Education to retire on 30 May 1938. Until she fled in June 1939 to her brother in Nice, she remained in her apartment at Trauttmansdorffgasse 19 in the 13th district.
The fate of the brother and sister during the Second World War is unknown. Marianne Zels lived from 1945 in Nice and died in 1957 while on vacation in Bad Ischl. A further sister Gertrud (Emmy) Stöger died in 1968 in Baden. In 2006, the Art Restitution Advisory Board recommended the restitution of the objects given to the Technisches Museum Wien in 1938 to the heirs of the Zels family.