Zach Parker is one of the playable characters in the Nintendo DS version of Call of Duty 4: Modern Warfare. The player starts as him in the mission "First to Fight" where he trains to be "battle ready" but is interrupted as the base is attacked by the OpFor. He manages to escape via Humvee. In the next mission, "Exodus", he uses the machine gun on top of the Humvee to fight off attacking OpFor members and one Mi-24. After that, he and the other Marines get off at a town and fight their way to the extraction point on foot. Eliminating snipers and fighting house to house, Corporal Parker and the other marines make it to the helicopter. In the mission "On Approach" Parker is a door gunner on a UH-60 Blackhawk named "Hawk 1". "Hawk 1" and another Black Hawk helicopter named "Hawk 2" go out and try to capture the "Bagman". During the mission, "Hawk 2" gets shot down by an RPG-7. A Marine rescue team is sent to get the downed crew while "Hawk 1" is ordered to keep going. Parker is a door gunner again with "Hawk 1" but this time he and the helicopter are sent to Russia to support a joint Marine and SAS raid on a launch facility. When they fly by the missile solo, they see the missile, appearing in "Missile Away", about to launch. Parker and a squad of Marines go in to try to stop it. As a T-72 tank attacks them, Parker calls in an air strike which destroys the T-72. Parker and the Marines fight their way into the control room and stop the launch. Parker, an SAS agent, and another marine get the nuclear secrets and drive away. Parker goes with another marine and their Humvee crashes. They then fight their way through the train yard until they find a pickup truck with a machine gun on the back bed. The two drive away to a bridge that is about to collapse. Corporal Parker and the other marine get out and sprint away before they fall off. The British SAS agent is lying wounded behind a destroyed car. Parker and the other Marine fight for their lives until a Blackhawk helicopter arrives, kills all of the enemies, and extracts Parker, the marine, and the wounded SAS agent.
Parker, promoted to Sergeant, returns in Call of Duty: Modern Warfare: Mobilized as a playable character. His new squad-mates are Sgt. Baker, and commanding officer, Captain Weston. After a failed attempt by the S.A.S. to capture a nuke, the Marines send a squad into an unnamed town after scanning for radiation with a UAV Recon. Fighting house to house, they deploy the Haz-Mat drone in 3 locations. When they arrive at House 3, they send in the Haz-Mat drone and try not to be spotted by the enemy guards. After a bit of stealth and some luck, the Haz-Mat bot picks up high levels of radiation. Parker and his squad breach the house and clear it. They realize that the nuke has been put somewhere else. The squad leaves the city in a stolen humvee after evading many APCs and soldiers. They get word of the nuke being held in some warehouses. After clearing both warehouses, they see the nuke being transported somewhere else. In a joint op by the S.A.S. and the Marines to capture the S.A.S. informant, Parker drives a tank to support the S.A.S. He subsequently gets picked up for a helicopter insertion to an oil rig to secure the nuclear device. After manning a minigun on the helicopter to provide support, he gets dropped off to secure a beach for transport. Having secured a transport, he gets on and Sgt. Baker disappears when they reach the oil rig. Arriving at the top of the cleared rig, the squad sees the nuke being flown away.
In the level "First to Fight", if the player approaches an instructor when they're not supposed to, that instructor will say, "What's your problem Corporal, you're not done in training yet!", which indicates that Parker is a Corporal.
It is possible to see Parker's face. In the campaign level "Needle in a Haystack", steer the HazMat robot up to Parker, and the player will see his face. Parker's appearance is the same as the player's allies.
Zach Parker is one if the few playable characters that are ranked Corporal.
In "On Approach", during the cutscene, it is possible the gunner is Parker. But, he could have the same model as the Allies, for most of them have the same models.