The following year he was engaged as an engineer with the Special Section of Railway Workers in Milan, then rose to a position in the newly formed Ministry of Communications in 1924, producing significant independent work by 1926.

He owed much of his success and influence to his intimate connections with the Fascist regime, and played a decisive role in using architecture to consolidate positive images of Fascism.

As chief architect for the Ministry of Communications and for the State Railways, both key modernizing sectors of Fascist rebuilding programs, Mazzoni designed many of them.

More recently academics and scholars such as Ezio Godoli, Giorgio Muratore, and Enrico Crispolti have begun a rehabilitation process and a critical re-evaluation of Mazzoni.

Stylistically eclectic, Mazzoni joined in 1933 to the so-called "second phase" of the Italian artistic movement Futurism, signing in 1934 the Manifesto of Aerial Architecture with F.T.

Trento had a special significance for the Fascist regime as the capital of the Trentino-Alto Adige (Welschtirol-Südtirol) region, annexed to Italy from Austria at the Treaty of Versailles after World War I. Trento's railway station represents Mazzoni's interpretation of the functionalist style typical of the times; the building's continuous windows and dynamic structural lines are said to express Futurist ideas of speed and streamlining.