To move from one success to another, you have to learn to unlearn. Take everything that helped you win the first time, then discard it and learn a new way. That's how Barry Diller, titan of "old" media (ABC, Paramount, Fox), mastered the new dot-com world—with everything from Expedia to Match.com. Part 2 of "Be an Infinite Learner." With Uber's Dara Khosrowshahi and serial entrepreneur Margaret Heffernan.