From The New York Times today:
But Mr. Zuckerberg has also been blunt about Facebook’s feelings on Apple. “We increasingly see Apple as one of our biggest competitors,” he said in an earnings call this year.
Even on that point, Mr. Cook has disagreed.
“I’m not focused on Facebook,” he told The Times this month. “I think that we compete in some things. But no, if I’m asked who our biggest competitors are, they would not be listed.”