This walkthrough will take the longer route to collect all the XOF patches in one go. The game has a ranked evaluation at the debriefing. You’ll get more score by completing the mission as fast as you can, not triggering combat alerts, not killing anyone, no retries, no reflex, not letting any helicopters get shot down and rescuing optional prisoners of war.
After starting the game, drop down to the ground and start rolling by going prone, then holding the Dash (L3) button from left to right. This should trigger a cutscene where an XOF patch will be thrown out from Snake's back. Pick it up to find the first XOF patch.
Now turn around and pick up the second XOF patch in the game near the edge of the cliff.
This is a stealth mission so to make your job a lot easier, avoid combat and do not unneccessarily kill enemies that can cause the whole to go on full alert. Before moving forth, use your binoculars and tag the guards so you can always take note of their location.
You can go through the gate or around the spotlight. When the spotlight is pointing away, run while keeping to the right and you'll run into a ledge you can climb on. Climb on it and take out the guard on the watchtower to disable the spotlight. You can now enter through the gate. Jump over the fence to the north and search the pile of trash to find the third XOF patch.
After getting the patch, carefully make your way to this refugee camp's northwest corner. You'll find prisoner there. Call in for a chopper exfil and order it to arrive from your starting position. Take note that the enemy movements will change and depending on how fast you move, you may encounter more patrols so adjust accordingly.
After reaching the warehouses, cross the road and crawl into the grass. There's a guard to the left but hold your fire since another guard will appear from a distance. Wait for the other guard to leave then tranq the nearby guard. Quickly pick up his body and hide it away. Next, continue north towards the warehouses.
There are two guards between the second and third warehouse. Stay behind the crate and let them leave. Now proceed north and you'll find some generators behind the fence. Pick the lock to open the fence gate. Climb the generator to your immediate left and pick up the fourth XOF Patch.
Now head east this time, just north of your objective area. There are several patrols hanging in and around the helipad. Make sure you tag the ones you spotted and carefully take them out, preferably by luring a few of them inside the landing zone. Two of such patrols will patrol inside but you can lure a few of them in by deliberately getting them suspicious. Once you're clear, continue heading east until you find a vacant guard house. The another XOF patch is found there.
From that guard house, you should now a few steps away from the prison area. Now take out any nearby guards then once clear, pick the lock. You should be able to pick up another XOF patch as soon as you open the gate.
Once you're all done, you can now proceed with the mission as needed. Once you've reached the prison camp, find Chico and unlock his cell for a scene. After the scenes, he'll give you Chico's Casette #3. There's also another casette in the cell behind his. (Here's to You)
You can bring him and the other prisoners to the rendezvous point BUT do not call for the helicopter yet and load them. This is necessary to get the correct events to trigger to get another casette tape. Be careful though since enemies will start converging near the prison area especially if you made a noise or if one of the guards called in reinforcements. There are four other POWs in other cages so you can free and carry them all to the RV if you want.
Now make your way to the Administration Building to the northwest. There's an SMG that you can swap your pistol behind the truck if you want to.
You head to the northern landing point to find more XOF patches. That area has a lot of open space so it will be a good idea tagging the enemies first and take out the spotlight. There are two ways to go around here; one is through the west which has a lot of open space but less guards or through the east with considerable cover and lots of guards. Going around to the east is recommended since the other XOF patches are found along the way.
Make your way around to the northeast to reach the landing pad. There's also a security camera on the way to the base's inner gate. You can blow it up to prevent yourself from being seen or get past under it. A Delta unit will arrive shortly to check the downed camera so make sure to knock out enemies as much as possible without being seen. If they failed to find you after a while, they will stand down. Find an XOF patch in the opening of the drainage system, behind some crates and boxes, a few distance away from the main door.
The next patch is located just inside the red door ahead. Climb up the generator units and leap to the ledge. Find the next XOF patch beside an exhaust tip.
Knock out the enemies especially the one guarding manning the watch tower. Once cleared, check the ground of the helipad with a black patch, beside an electrical block to the west to find this patch. If the area is too hot, you can come back later once you've knocked out the guy on the central tower.
Enter the admin building and make sure that there's no alarm or the enemies should be in normal status when you enter. You also need to get past the security camera in the northeast of the admin building instead of destroying it. You can do this by moving under its blind spot once it turns away.
Head to the boiler room where Paz is held and you should hear the three soldiers talking about a recording they threw away. As long as you don't alert any of them, they should have this conversation. Otherwise, you have to reload the checkpoint. Head to the northwest of the admin building and climb up to find Chico's Casette #5 in one of the dumpsters in the dead end alley beside the stairs.
Now make your way to the Central Tower. From where you got the casette, head south then climb the ladder leading to the platform along the wall to the east. Take out the guard there and pick up Chico's Tape #2.
You can now return to Paz and free her. Pick her up and you'll have to bring her back to the LZ. You have to put her down from time to time since she will make noises. There will also be more guards patrolling the area so take them out as necessary. Make sure to clear up the path before moving her since you'll have a difficult time reacting to enemies that may spot you.
There will be an armored vehicle waiting outside, depending on how much you've alerted the enemies. Move behind cover and go around. Once you're outside of its line of sight, make a run for it and make your way back to the RV. There are other nearby landing points in your location but they're hot so it will be a good option to just sneak around and make your way to the safest landing zone to the east.
There will be guards along the way so make sure you don't run in the open and use the bushes to go prone and hide. The landing point will have patrols so its up to you to take them out quietly or not. You can also call in the chopper when you're near so that you can just load Paz and the other prisoners once it arrives. Once done, ride the chopper to leave the area. Mission complete.
After completing the game, four side ops and one extra ops will become available. You'll also receive various rewards depending on your rank from completing the main mission, Ground Zeroes.