Czech left-hander Petra Kvitova reached the French Open quarter-finals for the first time in eight years as she overpowered China’s Zhang Shuai 6-2 6-4 on Monday. On yet another chilly day in the French capital, seventh seed Kvitova’s superior firepower proved decisive as she posted her fourth successive straight-sets victory. With so many big names already out, Kvitova will sense …