Kiefer-Zverev beat Americans Mardy Fish and Sam Querrey 4-6, 6-4, 10-1 on the second day of play in the tennis tournament.
Earlier Monday, German Philipp Kohlschreiber defeated American Robby Ginepri 6-7 (5-7), 7-6 (7-4), 6-0. Ginepri is appearing at his first tournament since undergoing an emergency appendectomy in late February.
Also, Sweden, four-time champion in this eight-nation round robin, beat France 2-1, Serbia beat three-time champion Argentina 2-1, and Italy beat 2008 runner-up Russia 2-1.
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