Daniels, who previously headed Facebook's business development team and had other roles, was named head of WhatsApp last May. He disagreed with some of the choices that were made to connect applications, said people familiar with his thinking. He also feared that Mr. Zuckerberg's plan would hurt the success of WhatsApp, particularly popular outside the United States.
As a result of these changes, Daniels resigned several months ago, said two people, although the decision was not made public until Thursday.
Cox has also been frustrated by Zuckerberg's decisions in recent months, some people said. Less than a year ago, Mr Cox held one of the most influential positions of Facebook as Product Manager, responsible for overseeing Instagram, WhatsApp, Messenger and Facebook.
Almost immediately, Mr. Cox ran into trouble, people said. Employees said he did not agree with some of Zuckerberg's ideas and product modifications, including the "Unified Messaging" project to connect applications.
But Mr. Zuckerberg had already made his decision. Cox informed Facebook of his decision to leave on Monday, according to a company report.
"It's been more than a decade since I shared the same message that Mark and I have always believed: the social media story is not written yet and its effects are not neutral," Cox said in his message. . "As builders, we must strive to understand its impact – all the advantages and disadvantages – and undertake the daily work of leaning it toward the positive and the good."
Mr. Zuckerberg encouraged others to take the place of those who left. Adam Mosseri, a long-time Facebook employee, was promoted to director of Instagram last year. On Thursday, Zuckerberg said Will Cathcart, another Facebook employee, would run WhatsApp, and that Fiji Simo would run Facebook's main application.