He had the ability to shoot highly pressurized air out of holes in each of his hands. With this ability, he could unleash pressurized air that can knock out or kill his targets and cause significant changes to the environment that he is fighting in. However, Zaku relies mostly on his ability to use pressurized air which makes him susceptible to an attack from someone who can move around swiftly like Sasuke Uchiha.
After a failed assassination attempt on Sasuke during a test, he lost during a preliminary battle in which both of his arms were severely wounded. Despite the severe damage, he was able to get his arms repaired and was able to pass the second portion of the Chuunin Exam.
During the third part of the Chunin exam arc, he fought against Shino Aburame. In their battle, Shino used his insects to cover up the holes that Zaku used in his arms to release air pressure. As a result, the air pressure within Zaku's arm caused him to lose both his arms and lose the battle altogether.
Before the invasion of the Leaf Village by both the sand and sound village, he and Kin were used as sacrifices by Orochimaru to summon the souls of the first and second hokage, Hashirama Senju and Tobirama Senju.