Miami — Britain’s Andy Murray moved into the third round of the ATP and WTA Miami Open on Saturday but Rafael Nadal, dizzy as he struggled to cope with heat and humidity, retired from his match. World number two Murray, twice a Grand Slam champion, downed Uzbekistan’s 76th-ranked Denis Istomin 6-3, 7-5 to reach the third round in a night match. “That second set was tight but I managed to get through it,” said Murray, who next faces Bulgarian 26th seed Grigor Dimitrov in his quest for a third Miami crown. Spanish fifth seed Nadal, a 14-time Grand Slam champion playing in the heat of the afternoon, feared for his safety and handed 94th-ranked Bosnian Damir Dzumhur a 2-6, 6-4, 3-0 triumph, stopping during a match for the first time in six years. World No. 1 Serena Williams ousted Kazak Zarina Diyas 7-5, 6-3, in the match after Nadal and [...]