Top seeds Alexander Zverev of Germany and American Coco Gauff advanced to the third round of the Canadian Open on Tuesday after both players were pushed hard by their opponents. World number three Zverev, playing in his first match since his first-round loss at Wimbledon, was far from his best but emerged with a 7-6(6) 6-4 win over Adam Walton under the lights in Toronto. Momentum shifted firmly in Zverev's favour when he won a 52-shot rally in the first set tiebreak, and he sealed the win on a