"Zero" received acclaim from music critics. Paula Carino of AllMusic described the song as "an exhilarating and wide-open expanse of pure electro-pop". Mary Bellamy of Drowned in Sound viewed the track as "the call to arms of a band who desperately want to teleport the refugees of fashion-fizzled pop, the hippest of hipsters and the weirdest outsiders to the dancefloor of their sweaty spaceship", stating it is "perhaps one of the band's finest moments ever committed to tape."
Slant Magazine's Jonathan Keefe praised "Zero" as "flat-out phenomenal", while Alex Fletcher of Digital Spy called it "a saucy electro romp that makes even GaGa seem a tad coy". Michael Hubbard of musicOMH dubbed the song "an all out visceral onslaught, a keening mix of battered synths, drum machines and Nick Zinner's typically bloodless guitar playing", and referred to it as "a mix of Show Your Bones' cleaner production with the grubbiness of the Is Is EP".PopMatters' Evan Sawdey opined that "[n]o YYY's song has ever been as disposable, replayable, or just outright fun as 'Zero'".
"Zero" was named the best track of 2009 by both the NME and Spin magazines. In October 2011, the NME placed the song at number thirty-nine on its list of the "150 Best Tracks of the Past 15 Years".
The music video for "Zero" was directed by Barney Clay and premiered on March 9, 2009. It was filmed in the San Francisco neighborhoods of Tenderloin, North Beach, and Chinatown. Speaking to Spinner, lead singer Karen O explained the concept of the video: "The visuals had to be well paced with the slow ecstatic build of the song. It made sense that the visuals would take you on a journey and keep you on the move—no sitting still for too long in the city landscape of bright lights, dark alleys and glittering streets. 'Zero''s sentiment is to revel in being you—you're a zero so screw it! It's the underdogs, the rebels, the outsiders that have always captivated me growing up so I decided why not flaunt that side of myself in the video."
The video opens with the band in the dressing room of The Warfield, getting ready for a show, at which point O walks through a curtain that takes her to the streets of San Francisco at night. Clad in a PVC dress and a studded leather jacket, O is seen walking around the streets and dancing atop cars. She soon joins her bandmates again as they perform the song in an alleyway. Towards the end of the video, the band play around with shopping carts in a supermarket, before playing in a local discount store.