Zanon de Castiglione, of Milan, succeeded in 1424, as Bishop of Lisieux, his uncle, Branda de Castiglione.

He was a celebrated jurist and professor at Paris, whom one finds frequently entrusted with embassies in France and Bohemia and who received his elevation as bishop at the hands of Martin V. In that year Zanon took the oath of loyalty to the church of Rouen.

On January 2.8, 1430, Zanon obtained expectations of being Bishop of Bayeux, to which he was transferred in 1432. In 1434 he was sent as a deputy of Henry VI to the Council of Bile; he departed with a commission from the Duke of Gloucester to buy for him all the books he could, especially those of Guarino of Ferrara and Leonardo Bruni.

He spent a year in Florence, singing the praises of his master to the Italians, who henceforth entered into relationships with his English patron. On July 1, 1441, Zanon was present with Pierre Cauchon upon the entry of the Duke of York into the cathedral of Rouen.

He replaced Cauchon on the King's Council in 1443 and he celebrated the requiem mass for Cardinal de Luxembourg. The following year he traveled about Lower Normandy with many other members of the Council to Provide the necessities of the country "for the good and honor of the King and his justice."

In 1445 Zanon came to Charles VII to treat of the marriage project between Edward of York and Jeanne of France, and that same year as dean of suffragans he was in charge of transmitting to the other bishops the orders for the convocation of the Council. The next year he was sent by Henry VI to the Sovereign Pontiff on the matter of the dispensing of commands, and he journeyed to Normandy with the commissioners of the King of England to assemble the members of the Estates "to have their advice upon the actions, maintenance and conduct of affairs of the seigneurie of the King."

In 1448 he inspected the situations and fortresses in the territories of Cotentin and Alençon, and he obtained from the English king delays for the inventory of the property of his See. When the English cause was lost, Zanon allied himself without difficulty with Charles VII, to whom he swore allegiance in November 3, 1449.

He was nominated Bishop of Pavia in 1453 and sent by Pope Calixtus III to the Council of Ratisbon to treat with the Emperor. Zanon was created Cardinal in 1456 and then created Papal Legate to the March of Ancona by Pius 11. He died suddenly of a fever at Macerta in 1459.

Italian in nationality, English at heart, and a man of the Renaissance, the opinion that he delivered concerning Jeanne, dated at Bayeux, is full of contempt.

This political bishop was not a Christian. But he was very well educated, and he must have been very greatly respected by all the Norman clerics as the nephew of Branda, who founded at Pavia in memory of all the benefits he had received in France, a college for the students of Lisieux, Bayeux and Evreux. Zanon was himself the first conservator of the privileges of the University of Caen.