Twenty-three times Grand Slam champion Serena Williams said she would have faced far harsher punishment had she engaged in similar behaviour to German Alexander Zverev, who was thrown out of a tournament last month for unsportsmanlike conduct. The world number three was kicked out of the ATP 500 event in Acapulco after he smashed his racket repeatedly against the umpire’s chair after a doubles defeat. Zverev was later fined $40 000 for the incident, in which he came perilously close to hitting umpire Alessandro Germani. “There is absolutely a double standard,” former world number one Williams …