Born in Paris, France in 1921, Zañartu moved to his native Chile in 1938, establishing himself as an artist.  In 1944 he traveled to New York to study with Stanley W. Hayter in the Atelier 17, becoming associate director of the studio in New York until 1949 and subsequently in the Paris studio from 1950 to 1957.  He taught printmaking, painting and drawing in various prestigious institutions.

He held numerous one man and collective shows in Europe, the United States and Latin America.  Solo shows include Galerie Springer, Berlin (1952), Pan-American Union, Washington DC (1956); Galerie Karl Flinker, París (1962), Instituto de Arte Contemporáneo, Lima (1963), Galería Buchholz, Munich (1967), and Retrospective 1946-1993 at the Galería Tomás Andreu, Santiago, Chile (1994).
Collective shows include the Sao Paulo Biennial (1957); the Tokyo Biennial of Graphic Art (1957), Internationale Grafik, Oldenburg Kunsteverein, Germany (1968), Artistes Latino-Americains de Paris, Grand Palais, París (1974), and Latin America and Surrealism, Bochum Museum, Germany.

His work creates the illusion of spaces of psychological tension through organic rather than figurative objects.