Niall Horan, Liam Payne, Harry Styles and Louis Tomlinson pose in a new photo to mark their new chapter in the band.
Last month, Zayn announced his decision to quit the band, just a week after pulling out of the world tour due to stress.
Zayn said in a statement: "I am leaving because I want to be a normal 22-year-old who is able to relax and have some private time out of the spotlight."
The new biography on the Modest! Management website does not reference Zayn, but it does detail the band's success, having "sold more than 50 million records, achieved a total of 91 number ones and performed to over 7.5 million fans worldwide".
Despite Zayn's departure, 1D said they would continue as a band, saying in a statement: "We're really sad to see Zayn go, but we totally respect his decision and send him all our love for the future."
As a four-piece, One Direction are now focusing on their world tour and fifth studio album.
Their boss, X Factor judge and music mogul Simon Cowell, said last week how Zayn's exit came as a "shock" but said for 1D, "the future's bright, I think."
One Direction rose to fame on the seventh series of The X Factor in 2010. They all applied as solo contestants, but failed to qualify for the Boys category. However, Simon and Nicole Scherzinger then put them together to form a band.
One Direction finished in third place and went on to achieve global success, making them one of the biggest boybands in the world.
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