Giovanni Battista Zeno
He was appointed a cardinal by his uncle, Pope Paul II on 21 November 1468, and named cardinal-deacon of Santa Maria in Porticu.[11] In the autumn of 1471, the government of Venice announced that it had uncovered a spy ring, which was passing on state secrets to the pope.[13] On 18 February 1477, Pope Sixtus IV wrote a letter to Doge Andrea Vendramino, thanking him for having Cardinal Zeno and Cardinal Giovanni Michiel placed in possession of their dioceses, and absolving him from the ecclesiastical censures which fell upon those who had deprived them of the income of their bishoprics.On the same day, Cardinal Zeno signed a document absolving the government of Venice of all moral and material blame for the sequestration of his benefices and the diocese of Vicenza.[15] In the papal consistory of 8 October 1479, Pope Sixtus IV promoted Zeno to the Order of Cardinal Bishops, and granted him the Suburbicarian diocese of Tusculum (Frascati).[16] Cardinal Zeno, Bishop of Tusculum, participated in the conclave of August 1484, as the loyal supporter of his cousin, Marco Barbo, who nearly succeeded in becoming pope.