Mrs. Ziff designs fine jewelry and founded Tamsen Z, an upscale jewelry boutique in New York. She is the widow of William B. Ziff Jr., the former head of Ziff Davis, a New York publishing company, who died in 2006. Mrs. Ziff, 64, pledged $30-million to the Metropolitan Opera, in New York, where she is co-chairwoman of the Board of Directors. She placed no restrictions on how the gift can be used. The donor’s connection to the opera company runs deep. Her mother, Harriet Henders, was an opera singer in the 1930s and ’40s, who made her U.S. debut at the Metropolitan Opera in 1939 in Der Rosenkavalier, by Richard Strauss. The opera did not disclose a payment schedule for the pledge. Mrs. Ziff also serves on the boards of the American Museum of Natural History, Carnegie Hall, Lincoln Center for the Performing Arts, New York Restoration Project, and the World Science Festival, all in New York, as well as Conservation International, in Arlington, Va., and Fairchild Tropical Botanic Garden, in Coral Gables, Fla.