Smith began playing bass in 1984 at the age of 14 after he and his high school (Torrey Pines High School, Del Mar, CA) friends were looking to form a reggae band, which they named White Lion (seemingly unaware of the heavy metal band of the same name). Smith attributes his sound to "being bored" playing single note basslines. Smith developed his sound by experimenting with different harmonies on the bass, a style that would later become his signature. Smith was largely self-taught and tried to do "different things with the bass" 

Born in San Diego, California, he first came to attention as the bass guitarist for rock band Three Mile Pilot. Smith's distinctive playing style and complex fretwork technique defines the overall sound of the band. This was clear as early as their first record Nà Vuccà Dò Lupù, on which Smith's bass was the only harmony instrument. Rumored attempts to change Three Mile Pilot's sound during the band's short tenure with major label Geffen Records persuaded Smith to separate from the band (and the label) and form Pinback with Rob Crow. Three Mile Pilot recently reformed and has released a new album, The Inevitable Past is the Future Forgotten. 

Pinback is a band formed and headed by Smith and Rob Crow in 1998. It is Smith’s most commercially successful project to date. Smith and Crow played music together as early as their days as roommates, and had never released any music. His break from Three Mile Pilot served as a good opportunity for the two to collaborate. Pinback often features Zach's innovative bass playing, with a unique layering of instruments, drum machines, and rich vocals. The band's original recordings, that later became their first album, This Is a Pinback CD, were recorded on Smith's personal computer. To date the band has recorded five studio albums, with the latest, Information Retrieved, released on October 16, 2012. The name “Pinback” originated from the 1974 film, Dark Star. One of the crew members on a spaceship in the film was named Sgt. Pinback. Systems Officer[edit] Zach Smith also has a solo project called Systems Officer that allows him "to follow through completely his own ideas and concepts" and "to explore the workings of his inner mind and let his ingeniousness flourish". Smith's own sound shines in this project, something not entirely possible in his other bands. However, listeners will find this sound fairly similar to his work with Pinback. On May 11, 2004 Zach released a self-titled EP from this project on Ace Fu Records, playing all instruments himself (including drums). In 2009, Smith released Underslept on the Temporary Residence Limited label, this time collaborating with Pinback and 3 Mile Pilot drummers Chris Prescott and Tom Zinser. A single with two B-sides, Shape Shifter, was also released. It is his first full-length album as Systems Officer. "When called upon to define [his] style, Smith demurs before answering. "I don't know. Pretty with an edge? I don't necessarily know how to explain it. I like dark and brooding tones. I don't ever want my music to get too pretty. I like it to have an underlying rawness. Sugar coating on the top, evil underneath. How's that? He plays Alembic Stanley Clarke bass guitars, set at a standard tuning.