Attilio Zanchi was born in 1953 in Milan. He began playing double bass in 1978 and spent two years in jazz courses at the Conservatorio Giuseppe Verdi in Milan under pianist Giorgio Gaslini, followed by three years at Milan's Civica Scuola di Musica. In 1979 he joined the Open Form Trio with keyboardist Piero Bassini and drummer Giampiero Prina, his first working group.

A 1980 scholarship took him to the University of Fine Arts in Banff, Canada, and to the Creative Music Studio in Woodstock, New York, where he studied bass with Dave Holland and improvisation with Karl Berger, George Lewis, Sam Rivers, Jimmy Giuffre, Ed Blackwell, Lee Konitz, Kenny Wheeler, Jack DeJohnette and John Abercrombie. In 1981 he performed at the Woodstock Jazz Festival alongside Baikida Carroll, Julius Hemphill and Ed Blackwell. Back in Italy, he joined the Milan Jazz Quartet and began what would become decades-long working relationships with Franco D'Andrea and Paolo Fresu; he is Discogs-verified as the bassist on D'Andrea's Quartet dates Live (1986, Red Record) and My Shuffle (1987, reissued with a live set in 1996), and as the regular bassist, alongside drummer Ettore Fioravanti, of the Paolo Fresu Quintet in its late-1980s lineup, documented on Paolo Fresu Quintet 1989 Live (issued 1992, Blu Jazz). From 1987 to 1997, per his own biography, he also worked regularly with singer Tiziana Ghiglioni, a relationship Discogs confirms at both ends of that decade: her Spellbound (1996, YVP Music) and, at the start of the run, his own leader debut below.

That debut, Early Spring (1987, Splasc(h) Records), doubles as a cross-section of the Milanese scene he'd spent a decade inside: alongside his own compositions and bass, its eight tracks bring in Franco D'Andrea and Paolo Fresu on the title track; Tiziana Ghiglioni, Stefano Battaglia and Fresu again on "After Hours"; and Ettore Fioravanti, pianist Roberto Cipelli and Fresu once more on "Dave" - three different quartets and quintets assembled under one leader credit. A year later, billed to the Attilio Zanchi Quartet, Cats (1988, also Splasc(h)) paired him with saxophonist/flutist Riccardo Luppi, pianist Massimo Colombo and drummer Christian Meyer; the session was later restored and archived by Rome's Saint Louis College of Music as part of its Jazz Archive project.

Zanchi was voted Best Italian Double Bassist in a 1992 Guitar Club magazine readers' poll, one of several such honors cited across his biographies without a single consistently sourced list of years. His profile abroad grew through the 1990s: he recorded with alto saxophonist Bobby Watson on an Italian-American all-star date, Bobby Watson (1991, Red Record/Musica Jazz, alongside Curtis Lundy, Victor Lewis, John Hicks and others), and toured with Watson's own quartet in 1997-1998; in 1999 he performed with vocalists Sheila Jordan, Nancy King and David Linx. His leader catalog through this period includes Music For An Imaginary Movie (1990, with pianist Massimo Colombo) and Some Other Place (1992); German-language sources credit the latter session to a lineup including Kenny Wheeler, John Taylor and George Garzone, though this could not be independently confirmed at the Discogs credit level for this profile and is noted here as attributed, not verified.

Four Ways (1997, Splasc(H) Records) paired him with American guitarist John Stowell, drummer Gianni Cazzola and vibraphonist Andrea Dulbecco, with Stowell contributing English liner notes. Encanto (2002) was a three-way billing with percussionist Naco and guitarist Bebo Ferra. In the mid-2000s Zanchi took part in a run of composer-tribute sessions circulating through the same Milanese post-bop circle - P.A.R.T.E. (Plays The Music Of Attilio Zanchi) (2005) turned the format on him, while he in turn played on tributes to pianist Roberto Cipelli, saxophonist Tino Tracanna and, most substantially, Thinking (Plays The Music Of Ettore Fioravanti) (2006, Blue Note/EMI) - a full album of Fioravanti's compositions, credited to the Paolo Fresu Quintet with Zanchi again on bass. The same year, Distanze (2006, Music Center) introduced the trio he would keep working in as Ars3, with pianist Mauro Grossi and drummer Marco Castiglioni, revisited on Promemoria (2010). F. à Léo (2007, Radio Fandango) was a five-way collective billing with Cipelli, Fresu, drummer Philippe Garcia and singer-songwriter Gianmaria Testa.

Ravel's Waltz (2015, Abeat Records) gathered several of his working groups onto one release, including the Fresu/Cipelli/Tracanna/Fioravanti quartet heard on the title track. City Of Dreams (For Garrison Fewell) (2017, Abeat Records), with harmonica and accordion player Max De Aloe and guitarist Lorenzo Cominoli, was a tribute to the American guitarist Garrison Fewell, who died in 2015 and whom all three musicians had personally known; liner notes came from guitarist Pat Martino and from Paolo Fresu. Zanchi founded a septet dedicated to the music of Charles Mingus, Portrait of Mingus, in 2007; the project's studio recording, Mingus Portrait, appeared in 2024 on Mono Jazz with saxophonist/flutist Gianni Azzali, trombonist Andrea Andreoli, trumpeter Daniele Nocella, pianist Massimo Colombo and drummer Tommy Bradascio, and the group performed at Milan's JazzMI festival in 2023 and at Serbia's Nišville International Jazz Festival.

Alongside performing, Zanchi has taught jazz specialization courses at conservatories in Naples, Potenza, Trieste, Brescia, Vicenza, Piacenza and Milan since 1997, and has taught improvisation and ensemble music at Milan's Cluster Music School since 2022. He has authored instructional books including Enciclopedia Comparata degli Accordi e delle Scale and Inside The Standards. Press biographies describe a catalog of more than 100 recordings and well over 1,000 concerts; the one number this profile can anchor directly is the 149 total artist-relationship credits (15 as leader or co-leader, the rest sideman, producer and compilation appearances) that Discogs documents on his own artist page as of this writing.

Zanchi's foundation sits at the intersection of two distinct educations: two years of Milan Conservatory jazz courses under Giorgio Gaslini, and a formative year inside America's free-improvisation circuit at the Creative Music Studio, studying with Dave Holland and playing alongside Sam Rivers, Julius Hemphill and Ed Blackwell. That double grounding shows in a catalog that runs from the open, collectively-composed language of his earliest sideman dates to the harder-swinging, tune-based post-bop of his Franco D'Andrea and Bobby Watson associations and the Charles Mingus repertoire of his current septet. As a leader, his own records lean toward a compositionally driven, Milanese post-bop idiom, frequently built around rotating quartet and quintet casts drawn from the same circle of Splasc(h)- and Abeat-affiliated musicians he has worked alongside for decades.