Question: Are both Johnnie To and Howard Zieff directors?

Documents:
source: Howard Zieff
text: Howard Zieff Howard B. Zieff (21 October 1927 – 22 February 2009), (pronounced Zeef ) was an American director, television commercial director, and advertising photographer.

source: Johnnie To
text: Johnnie To Johnnie To (born 22 April 1955), also known as To Kei-Fung (杜琪峯), is a Hong Kong film director and producer. Popular in his native Hong Kong, To has also found acclaim overseas. Intensely prolific, To has made films in a variety of genres, though in the West he is best known for his action and crime movies, which have earned him critical respect and a cult following (which include Quentin Tarantino, who once said that he really loves to watch To's gangster films).

source: House Calls (1978 film)
text: House Calls (1978 film) House Calls is a 1978 comedy-drama film starring Walter Matthau and Glenda Jackson, directed by Howard Zieff.

source: Unfaithfully Yours (1984 film)
text: Unfaithfully Yours (1984 film) Unfaithfully Yours is a 1984 American romantic comedy film directed by Howard Zieff, starring Dudley Moore and Nastassja Kinski and featuring Armand Assante and Albert Brooks. The screenplay was written by Valerie Curtin, Barry Levinson, and Robert Klane based on Preston Sturges' screenplay for the 1948 film of the same name. The original music score is by Bill Conti and the song "Unfaithfully Yours (One Love)" was written for the film and performed by Stephen Bishop.

source: My Girl (film)
text: My Girl (film) My Girl is a 1991 American comedy-drama film directed by Howard Zieff and written by Laurice Elehwany. The film, starring Macaulay Culkin and Anna Chlumsky in her feature film debut, depicts the coming-of-age of a young girl who faces many different emotional highs and lows. The film also stars Dan Aykroyd and Jamie Lee Curtis.

source: The Main Event (1979 film)
text: The Main Event (1979 film) The Main Event is a 1979 American sports romantic comedy film starring Barbra Streisand and Ryan O'Neal, written by Gail Parent and directed by Howard Zieff.

source: The Dream Team (film)
text: The Dream Team (film) The Dream Team is a 1989 comedy film directed by Howard Zieff and produced by Christopher W. Knight for Imagine Entertainment and Universal Pictures. It stars Michael Keaton, Christopher Lloyd, Peter Boyle and Stephen Furst as mental-hospital inpatients who are left unsupervised in New York City during a field trip gone awry. Jon Connolly and David Loucka wrote the screenplay.

source: Jonathan Kaufer
text: Jonathan Kaufer Jonathan David Kaufer (March 14, 1955 – October 2, 2013) was an American film director, screenwriter, and occasional actor. Kaufer received his first job while in his late teens as a writer for the sitcom "Mork & Mindy". Filmmaker Howard Zieff later hired Kaufer to do rewrites for his films, and his work on the 1979 film "The Main Event" led to a development deal enabling him to direct his first film, the romantic comedy "Soup for One". At the time, he was the youngest director hired by a major studio.

source: Hearts of the West
text: Hearts of the West Hearts of the West, released in Europe as Hollywood Cowboy, is a 1975 comedy film directed by Howard Zieff, and starring Jeff Bridges, Andy Griffith, Blythe Danner, and Alan Arkin. Set in the 1930s, the story revolves around a wannabe Western writer who finds himself cast as a leading man in several B-movie westerns.

source: Slither (1973 film)
text: Slither (1973 film) Slither is a 1973 American comedy film starring James Caan. It was directed by Howard Zieff.

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Answer: yes