She collaborated with artists such as Madonna and the Ying Yang Twins, while contributions came from a wide range of producers, including Bloodshy & Avant, R. Kelly, Trixster, Moby, Guy Sigsworth and the Matrix.

A global commercial success, it debuted atop the US Billboard 200 with first-week sales of 609,000 copies, making Spears the first female artist to have her first four albums reach number one.

"Outrageous" was plagued by a lack of promotion due to Spears injuring her knee while filming its accompanying music video, and only peaked at number 79 on the US Billboard Hot 100.

"[11] On August 27, Spears opened the 2003 MTV Video Music Awards by performing a medley of "Like a Virgin" and "Hollywood" with Madonna, Christina Aguilera and Missy Elliott.

[13] Madonna then emerged from the cake wearing a black coat and a hat and started singing "Hollywood" before proceeding to kiss Spears and Aguilera on the lips.

[16] For In the Zone, Spears worked with hit producers such as Bloodshy & Avant, R. Kelly, Diddy, Christopher Stewart, Moby, Guy Sigsworth and the Matrix.

"[18] Christopher Stewart and Penelope Magnet, known collectively as RedZone, presented Spears with the third song they had written and produced, titled "Pop Culture Whore".

"[1] RedZone were then enlisted to work on several more songs for the album, including co-writing "Early Mornin'", recording background vocals for "Outrageous" and producing "The Hook Up".

[19] Spears talked about the overall sound of the album with Rolling Stone, saying: "I'd describe it as trance-y, kind of vibe record—something you could listen to that's no so song-structured [...] Of course I'm not doing '...Baby One More Time' and those massive hits anymore.

[29] Caroline Sullivan of The Guardian deemed In the Zone "a happy collision of house, dreamy electro-pop and Britney’s lyrical preoccupations [...] which have her perched on the cusp between teen poppet and sexually confident woman.

[1][26][31] "Showdown" has "bubbly" beats and its lyrics, about "fighting and making up with carnal relations", include the lines "I don't really want to be a tease / But would you undo my zipper, please?"

[33] On the Euro trance and ambient-techno song with trip hop influences, Spears sings: "Oh, it's so hot, and I need some air / And boy, don't stop 'cause I'm halfway there" and "Just put your lips together and blow.

[34] It contains elements of hip hop, electropop, and bhangra music, and features varied instrumentation, such as drums, synthesizers, high-pitched strings and surf guitars.

"[41] The Rishi Rich's Desi Kulcha Remix of "Me Against the Music" removes the original melody of the song and adds a clattering backbeat and Punjabi shouts.

[44][45] On September 14, Spears played a surprise concert at Rain Nightclub in the Palms Casino Resort, and performed "Me Against the Music", "Breathe on Me" and a medley of "...Baby One More Time" and "I'm a Slave 4 U".

[53] In November 2003, Zomba Label Group president Barry Weiss had spoken to Billboard and said that In the Zone was being promoted on a global level, exhausting areas such as print and electronic media, television, radio and video to raise awareness of its release.

Other broader-based marketing efforts included a tie-in with marketing company LidRock, where after ordering a soda at Sbarro, customers received a cup featuring the artwork and a three-inch disc in the lid featuring "Brave New Girl" and songs by two other artists; in December, an updated LidRock disc was made available, including a remix of "Me Against the Music" without Madonna, as well as songs by fellow Jive acts Nick Cannon and Bowling for Soup.

[64][65] "Me Against the Music" achieved international commercial success, peaking atop of the charts in countries such as Australia, Denmark, Hungary, Ireland and Spain, as well as the European Hot 100 Singles.

[66] Directed by Joseph Kahn, the accompanying music video for the song portrays Spears as a secret agent in the search of a vial of green liquid.

[66][75] Its accompanying music video, directed by David LaChapelle, portrays Spears as a star hounded by paparazzi, who drowns in her bathtub when she starts bleeding from a wound in her head.

[66] Directed by Dave Meyers, its accompanying music video was being filmed in New York City on June 8, when Spears injured her knee and had to undergo arthroscopic surgery.

"[64] Ruth Mitchell of the BBC called "Early Mornin'" the best track from the album, but added: "Sadly, her attempts to prove her new-found maturity are what overwhelm and cloud all that is good about In The Zone.

"[65] David Browne of Entertainment Weekly called "Brave New Girl" and "Touch of My Hand" the best and most straightforward moments of In the Zone, but added that "On a CD intended to celebrate her lurch into adulthood, Spears remains distant and submerged.

"[85] Sal Cinquemani of Slant Magazine stated: "Britney's fourth album, In The Zone, finds the pop tart coming of age with a bold mix of hip-hop and dance music, wiping clean the last traces of her bubblegum-pop past.

"[28] Dorian Lynskey of The Guardian commented: "Unlike previous Britney albums, In the Zone has no filler and no shoddy cover versions, just 57 varieties of blue-chip hit-factory pop.

"[64] Sal Cinquemani of Slant Magazine stated: "For a girl who's always seemed too sexed-up for her age, In the Zone finds Britney finally filling her britches, so-to-speak.

"[38] Following the abrupt conclusion of the Onyx Hotel Tour due to her knee injury, Spears embarked on a prolonged hiatus from performing,[114] and would not release another studio album until Blackout in October 2007.

"[17] Celebrating the album's 15th anniversary in 2018, Jason Lipshutz of Billboard claimed it "signaled a more mature direction for Spears as she explored electronic music and hip-hop like never before.

And the record's lyrics — which referenced her breakup with Justin Timberlake and pushed back at her critics in the media — celebrated new levels of independence and candor for the singer.

"[122] Los Angeles pop-up museum The Zone, celebrating Spears' "iconic songs, videos, and outfits through Instagram-worthy photo ops, interactive displays and personalized content activated by special RFID wristbands", was titled after the album and opened in January 2020.