Zahirnejad began studies in the Imam Ali Military University in 1951.

After the Iranian Revolution, he returned to the army at the beginning of the unrest in Kurdistan and he became the commander of 64th Infantry Division in the same year.

In 1980, he was promoted to brigadier general to command the Iranian Gendarmerie and Army.

On 9 October 1981, he was promoted to the position of President of the Joint Chiefs of Staff.

During the Iran–Iraq War, his insistent implementation of regular military commanders and conventional tactics led to clashes with the Iranian Revolutionary Guard Corps (IRGC), a branch of the Iranian Armed Forces that relies on the use of mostly light infantry together with some armored equipment as well as unorthodox military tactics.