 In 1240 he helped Doge Jacopo Tiepolo during the siege of Ferrara, in 1242 put down a revolt in Zara and in 1244 he was named "capitano generale da Mar" (fleet commander) of the Republic of Venice.He was also the "podestà" (Chief Magistrate) of numerous Italian cities.After the death of Marino Morosini, Zeno, who was then "podestà" of Fermo, was elected Doge with 21 out of 41 votes.