Top-seeded Alexander Zverev toughed out two tiebreaks to beat Alexander Bublik 7-6 (8/6), 4-6, 7-6 (7/1) at the Shanghai Masters on Tuesday, winning his first match since being guaranteed the year-end world number one ranking. The 29-year-old German will play Alex de Minaur in the quarter-finals. “Really difficult match,” Zverev said. READ: Alexander Zverev clinches