Zennaro has been coaching since 2007. In 2010, he began working with the Italian Junior National team as a foil coach and worked with the team through 2017.
Prior to his coaching career, Zennaro was a successful foilist, winning numerous individual and team titles. In 1998 he won gold at the Italian Championships and an individual silver medal at the World Championship in Seoul the following year. He earned a second gold medal at the Italian Championships in 2004 and finished second at the Mediterranean Games in 2005. In team competition, he was a member of the gold medal team at the 2002 European Championships in Moscow.Zennaro also had the opportunity to bring his talents to the Olympic stage. At the 2000 Summer Olympics in Sydney, he was a part of the Italian foil squad that took home a bronze medal.