[2] He was a canvas and fresco painter of biblical and religious subjects who worked in a late Mannerist style.
He was apprenticed in Rome during the papacy of Gregory XIII and worked on numerous fresco cycles under pope Sixtus V, such as the Loggia della Benedizioni in the Lateran Palace, the frescoes on the walls and vaults of the Scala Santa of the adjacent Basilica of San Giovanni in Laterano, and the decoration in the Sistine library.
Among his most important works of his late period are The Pool of Bethesda, made around 1600 for the confraternity of San Giovanni Decollato.
In 1640, Cardinal Girolamo Colonna made Fenzoni a knight in the Order of the Golden Spur (cavaliere dello speron d’oro).
His style was influenced by the artists working for the court of Rudolf II in Prague who are referred to as Northern Mannerists.