From Battlestar Wiki, the free, open content Battlestar Galactica encyclopedia and episode guide
Zephyr has many noticeable and unique features that sets it apart from other fleet ships.
The most noticeable feature, is the ships ring. Spinning counter-clockwise to "create" its own gravity, the ring is home to a biological habitat, populated with trees, water, and buildings for visiting Colonials to utilize and enjoy. The habitat is enclosed by a glass facade, which leaves an interesting view of the aft end of the ship, and on to the other side of the ring to anyone looking up. The ring is supported by four main pylons which connect the ring to the rest of the ship.
During the Cylon siege in the Ionian Nebula, the ring is struck by two Cylon missiles, and severely damaged with great loss of life. After making an escape, crews begin to repair the damage, and within two months, the ring was back in working order (TRS: "Six of One" "Guess What's Coming to Dinner?").
The second noticeable feature is the ship's sublight engines. Compared to the more traditional chemical thruster boosters of other fleet ships, Zephyr has an engine assembly which closely resembles that of an electric powered drive.
Zephyr has played an important role in the fleet, since the Fall of the Twelve Colonies. During the events of President Laura Roslin's incarceration, the ship hosted the Quorum of Twelve (TRS: "Fragged").
Lt. Felix Gaeta discovers fraudulent ballots for President Roslin in Zephyr's ballot box during her ill-fated re-election attempt versus Vice President Gaius Baltar. The ballots are later rejected and Baltar is declared the winner (TRS: "Lay Down Your Burdens, Part II").
Zephyr is among the first ships taken through the star cluster towards the algae planet (TRS: "The Passage"), and is home to Baltar's first lawyer, Alan Hughes, as Baltar was previously recaptured on the algae planet. Racetrack complains that she has to shuttle him between there and Galactica (TRS: "The Son Also Rises").
As the Cylon rebels begin integrating with the surviving Colonials, Junior Lieutenant Felix Gaeta is on his way to the Zephyr for some R&R along with two Number Eights, Specialist Brooks, Lt. J. "Shark" Finnegan and "Easy" Esrin when an emergency jump and a malfunction separate their Raptor from the rest of the Fleet, with deadly consequences (TRS: "The Face of the Enemy").
As Galactica prepared for one last fight, the ship was left with the rest of the fleet with the Rebel Basestar, the new flagship of the fleet. After Galactica returned, the ship jumped to what would become the Colonial's new home, Earth. After the population is offloaded the ship is later guided by Anders into Sol. (TRS: "Daybreak, Part II").