German tennis star Alexander Zverev has trained with 98-year-old Ukrainian player Leonid Stanislavskyi as he boosts his fitness ahead of the Davis Cup this week. The Olympic champion has been out injured since a foot injury at the French Open three and a half months ago but will return in Hamburg in the group stage against France, Belgium and Australia from Tuesday. Stanislavskyi, who came to face Zverev in Hamburg, is the oldest active tennis player in the world according to Guinness World Records. Zverev’s parents are Russian but he supported the decision of the governing ITF to exclude Russ…