Volkart-16. Has anyone information on my Mother's siblings and her maternal parents (my Grandparents)?

Question

My Mother Martha Volkart (maiden name) was born in Windlach, Zuerich, Switzerland in 1913, died 1975 and was married to my Father Theophil Keller (Keller-4564), born in Zuerich, Zuerich, Switzerland in 1911. Died in 1988. To be noted is that my Grandparents never emmigrated. If it helps, please check out: https://www.myheritage.de/site-family-tree-239982261/keller