After service in World War I Muzio began his practice in 1920 and is responsible for the best-known work of the Novecento movement, the 1922 residential block called the Ca' Brutta ("Ugly House") on the Via Moscova in Milan.

The five story apartment building was erected on a rounded corner patterned with real and blind arches, empty niches, and varying bands of horizontal color.

In 1927-29, collaborating with Alberto Alpago Novello, Tomaso Buzzi, Ottavio Cabiati, and Gio Ponti, Muzio designed the shrine for those fallen in the World War, the Tempio della Vittoria adjacent to the Basilica Sant'Ambrogio.

[2] A notable project by Muzio is the design of the Basilica of the Annunciation in Nazareth, completely rebuilt between 1960 and 1969.

In 1960 he built the Edificio Beni Immobili at the corner of Vittorio Emmanuele and Via privata della Passarella in Milan, incorporating the Art Nouveau facade of the Magazzini Bonomi.