Zim was born 1909 in New York City, but spent his childhood years in southern California. At the age of fourteen he returned to the east, and took his degrees (B.S., M.S., Ph. D.) at Columbia University. Zim wrote or edited more than one hundred scientific books, and in a thirty-year career teaching in the public schools, introduced laboratory instruction into elementary school science. He is best known as the founder, in 1945 (and for twenty-five years, editor in chief) of the Golden Guides, pocket-size introductions for children to such subjects as fossils, zoology, microscopy, rocks and minerals, codes and secret writings, trees, wildflowers, dinosaurs, navigation and more. He was the sole or co-author for many of the books, which were valued for their clarity, accuracy and attractive presentation—helped by the illustrations of his friend, Raymond Perlman.

He moved to Florida with his wife, the anthropologist Sonia Bleeker, and continued to work on the Golden Guides series until Alzheimer's disease forced him to slow down in the 1990s. He died in 1994 at Plantation Key, survived by his second wife, Grace Shows, and two sons.