However, the King wasn't discouraged by the failure and the following year, he managed to obtain from Pope Martin V a different diocese to him, Trento, who was located on the border between Italy and Germany.

With the help of Emperor Sigismund, in 1435 he was able to finally resolve the conflict with Tyrolean ruler Frederick IV: Alexander agreed to recognize the overlordship of Tyrol in return for which was guaranteed the territorial integrity of his Bishopric.

Shortly after, his active foreign policy and the designation of several Polish in several of the Bishopric offices, caused the rebellion of the local clergy, and almost lost the power.

Alexander's support to the Council of Florence (he even personally attended in the sessions at Basel in 1433, 1434 and 1442), brought him in December 1439 the title of Patriarch of Aquileia, while he kept the dignity of Bishop of Trento.

Antipope Felix V didn't have sufficient support to implement this decision, while his opponent, Pope Eugene IV appointed to this office another candidate who actually won the power, Ludovico Trevisan.

Soon after, the Council and Felix V (in order to bring the Jagiellonians and Habsburgs to their side), granted Alexander the title of Cardinal with the diocese of St. Lawrence at Damascus (12 October 1440), the Swiss Bishopric of Chur (March 1442) and finally the rectory of St. Stephen's Cathedral in Vienna.

In addition to this rich prebends, he also received from the council important diplomatic missions, but the war against Venice prevented him to participate in the Sejms of Nuremberg and Mainz, or in the disputes between Austria and Poland for the Bohemian throne.