Objective 1: Exterminate The Enemies Heading For The Radio Station
This is a hard one. When you get close to the first enemy compound shoot those enemies on the roofs especially those with RPGs followed by the enemies on the ground. There's also some enemies near the first truck so you might as well shoot that.
Objective 2: Get Priboi's Briefcase, And Eliminate Zaleb
You'll pass another convoy with RPG armed men, just shoot the barrels beside the trucks and they will explode along with the enemies near them. You'll pass another building shoot the barrels at the front door and kill the enemy on the roof. After that is Zaleb's Compound, shoot the guards at the watchtowers and the enemies on the roofs. Shoot the vehicles as well. After you land shoot the rest of enemies on the ground and enter Zaleb's building. Zaleb and Priboi's briefcase is on the second floor. Use your thermal goggles to know where guards are located in each rooms.
Objective 3: Get Back To The Helicopter With The Briefcase
After you killed Zaleb and his posse get the briefcase and climb up coz other guards are advancing below. Once on the rooftop jump on the southern side of the building and run around far from the compound leading back to the road and your Helicopter.