An older model of the MS-06 Zaku II, the Zaku I has less mobility and overall inferior performance to his successor, but is still adequate for sniper operations that do not require great mobility, such as the operations undertaken by Zeon's Living Dead Division. In addition, it is equipped with a specialized backpack to allow for movement in space.
Shortly after the appearance of the FA-78 Full Armor Gundam, Daryl Lorenz was issued a Zaku I due to a shortage of working mobile suits in the Living Dead Division. During a skirmish in the Thunderbolt Sector, Daryl nearly destroyed the Gundam with a Big Gun blast, but a bolt of lightning narrowly blocked the beam attack. The Zaku I was severely damaged by the Gundam before using a Cracker grenade to escape. Daryl lost his left hand during the battle.