When Alibaba Group Holding Ltd’s (BABA.N) eccentric founder Jack Ma stepped down as CEO two years ago, he declared “the Internet belongs to young people,” and promised that most of the company’s leaders born in the 1960s would soon retreat from management. On Thursday, that transition at the e-commerce behemoth appeared complete as Ma trumpeted the appointment of a fresh chief executive, Daniel Zhang, born in 1972, as part of a broader reshuffle.