Extract the juvenile fighters from Masa village
Unarguably, this is the most demanding secondary objective of this mission. It requires flawless operation and it is best to complete it on your replay of the mission. Start by reaching Bwala ya Masa village. Explore its central part, where you should notice the juvenile fighters shown in the above screenshot, being trained by at least two rebels.
Use any suppressed weapon you eliminate the grown-ups quickly. The kids should start escaping and you need to prevent them from doing that, before they leave the map. Depending on what you have in your inventory, you can start restraining the juveniles at a distance (e.g. the sniper rifle with sleeping ammo) and shoot at them. After you finish, make sure that you have all four of them on the ground. Mark this spot to make it easier for you to return here in the future.
Unfortunately, it is impossible to use the fultoning device on kids. Therefore, take a look around on the nearby hill, where you should find a jeep. Deal with the enemies here, steal the vehicle and drive back to the children. At the same time, request the helicopter pick-up from where you started this mission.
Now, there are two things you can do. If you have the CARGO 2 upgrade, load the kids into the jeep (which is its maximum capacity), fulton the car and deliver the last kid to the landing zone. IF you still do not have the upgrade, drive all the kids to the landing zone. Since you need to do this twice, clear the village of the enemies beforehand.
Extract the vulture from the burnt-down village
You can find the rare vulture species on your first playing of the mission and this is not too trouble some. Pick the Western road towards Mfinda Oilfield. Soon before you reach your destination, you walk into the burnt-down village. Use binoculars (or the help of the D-Dog) to locate the vulture shown in the above screenshots. Crawl and sneak up to the bird. Then, use any weapon with sleeping ammo. Finally, fulton the vulture to the Mother Base.
Extract four walker gears from the premises of the oilfield
enemies using walkers appear only as late as towards the end of the mission, i.e. right after you have destroyed the tank in Mfinda Oilfield. Right after you destroy the tank, reach the road to the South of the base and wait for two, out of four, walkers to arrive. Sneak up to them from behind and use any weapon to incapacitate or kill the operators. After you do that, fulton both of the walkers, where it is only possible if you have the CARGO 2 upgrade (and the money to cover the expenses connected with fultoning).
To find the other two walkers, head towards the road to the East of the oilfield (the one towards outpost 01). The walkers here are accompanied by regular soldiers, whose attention you can distract or neutralize, since you are here. Regardless of which you do, do not use heavy weapons to prevent destroying the walkers.