The Azzurri’s 119-cap flanker Zanni, 36, was applauded by teammates and staff with not more than 200 people authorised to be present at the the game behind closed doors at the Stadio Comunale Monigo
Neither side had anything left to play for in the penultimate round of the re-organised season, with Zebre always in control, leading 10-3 at half-time in hot conditions, to end a run of five consecutive defeats to their local rivals.
Tommaso Boni and Jimmy Tuivati both touched down for Parma side Zebre with Carlo Canna kicking five points and Antonio Rizzi two.
Treviso paid for their indiscipline and the inexperience of many young players with Joaquín Riera scoring their only try late.
Ian Keatley converted with rookie Paolo Garbisi also on target for the hosts.
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