Germany’s Olympic champion Alexander Zverev has called for reform of the ATP tennis calendar to provide players with more rest and made a concrete suggestion for improvement. “After the US Open, another Masters, a 500 level tournament and the finals, then we’re done at the end of October,” the world number three told the Bild am Sonntag paper. “The body already needs two months to recover.” Zverev is in Turin for the season-ending ATP Finals and will go on holiday from next Sunday, after the final at the latest. “I’ll start again with training in early December,” he said of the Australian Open…