How to Zoomin and ZoomOut in appium1.8.2

Support
1

Using Touch-Action, but nothing happened

my code

def zoom(self):
    x1 = self.x / 2
    y1 = self.y / 2
    action1 = TouchAction(self.driver)
    action2 = TouchAction(self.driver)
    zoom_action = MultiAction(self.driver)

    # action1.tap(loc, x1, y1).release().perform()

    action1.long_press(x=self.x * 0.4, y=self.y * 0.4, duration=2000).move_to(x=self.x * 0.1, y=self.y * 0.1).wait(500).release()
    action2.long_press(x=self.x * 0.6, y=self.y * 0.6, duration=2000).move_to(x=self.x * 0.8, y=self.y * 0.8).wait(500).release()


    print u'start zoom...'
    zoom_action.add(action1, action2)
    zoom_action.perform()