Francesco Zabarella

The Paduan Government repeatedly employed him on diplomatic missions, and towards the end of 1404, he was one of two ambassadors sent to King Charles VI of France to obtain the latter's assistance against Venice, which was preparing to annex Padua.

On 18 July 1410, Pope John XXIII appointed him bishop of Florence and papal referendary, and on 6 June 1411, he made him the Cardinal Deacon of the Titular church of Santi Cosma e Damiano .

Zabarella's chief writings in canon law are (with examples of editions): Also attributed to him but in need of verification: A large number of his letters are in the Österreichische Nationalbibliothek of Vienna, Cod.

Ciconia complimented Zabarella in song, by composing a three-voice isorhythmic motet in his honor, Doctorum Principem/Melodia Suavissima/Vir Mitis, surviving in the manuscript Bologna Q15.

Though he never received major orders, he was one of the most active and influential cardinals of the Antipope John XXIII, whose interests he supported at the Council of Rome (1412–13).

When this council failed to end the lamentable schism, John XXIII sent the cardinals Zabarella and De Challant as legates to King Sigismund (son of Holy Roman Emperor Charles IV, and emperor after 1433) at Como in October, 1413, with full powers to come to an understanding with the latter concerning the place and time for holding a new council.