When the initial cut scene ends, take out your binoculars and scout the area. Focus on targets for an extra second to mark them. Once they are tagged, you can see their locations even if they happen to be on the other side of a wall. Look for three guards (although you might see more in the distance), one in the tower and two by the gate.
Before taking the shot, head to your right and climb up onto a path. You should have a clear line of sight on the guard in the tower. Take him out with a tranquillizer headshot before continuing along the path.
When you enter the facility, take cover to avoid the oncoming jeep. Turn right and head to the east towards the area where the prisoners are being held.
As you approach the facility, you'll encounter a guard post with at least three guards. Two will be inside a building and the third is outside keeping watch. Neutralize each of them with tranquilizers and hide the bodies. Always be sure to stay in cover and avoid the spotlights.
Continue to move east towards where the prisoners are being held. There's a lone guard at the entrance of this section. Take him out with a tranquillizer and stash the body inside the booth nearby. Keep on the path towards where Chico is being held. Two more guards patrol this area, one inside and one outside. Observe their paths and neutralize them the same way. Avoid shooting through fences, since it increases the chance of being detected.
With the coast clear, rescue Chico and take him along the path that leads towards the beach. Call in your extraction helicopter to complete this objective. If you don't want to alert enemies to your presence, make sure not to select any music for your helicopter to play as it flies in.
Listen to the tape that Chico gave you before heading back in to rescue Paz. As you move back the way you came, hop into the back of the truck parked at the security booth. This will help you infiltrate the admin area where Paz is being held.
Jump out of the truck just before it stops backing up into its spot. Be careful of the guard driving. You can tranquilize, melee or leave him alone. The choice is completely up to you.
There aren't as many guard towers and spotlights to concern yourself with in this area, so be careful of the guards and the security cameras. You can shoot the cameras to disable them, but even this raises suspicion and will cause a guard to investigate. Sneak around the back of the building where the truck parked to avoid the cameras.
Move quietly towards the guard in front of the smaller buildings. Melee and pull him back into the shadows to avoid having the cameras spot you. Be mindful of the two guards that remain.
Take the yellow stairs to the lower level to move closer to where Paz is being held. Near the entrance, there is one guard outside and two more inside. Flank them using the boilers and hit all three with your tranquillizers. Once they're neutralized, there are no more guards to deal with. Move to the end of the hall, take a left and then a right to reach Paz's cell.
Once you have Paz on your shoulders, there will be three more guards on the path back. Put Paz down and take out the first guard. Sneak around the boilers again and take out the remaining two guards near the exit.
With Paz on your back, the route you took to enter the main building isn't a good option. Instead, take the main courtyard, avoiding security cameras and putting Paz down to deal with guards as you go.
Once you're out of the gate, call in the helicopter for extraction. If you call it into a Landing Zone (LZ) in a highly exposed area, there's a chance it could be shot down. Think about calling in an extraction at the point you entered or even back where you evacuated Chico.
An alternate way out is to slip into the vehicle outside the main building and drive past everyone. You will be detected and shot at, though. If you choose this option, call the extraction in the same place you took Chico.
Either way, once onboard, the helicopter provides a bit of cover fire as you extract.
Nice work! You completed the campaign portion of Ground Zeroes. Grab a snack and enjoy the cut scenes.