The best strategy to snag those 3 stars in MT Zaya to get the King of The Mountain trophy.
All you need to do is finish all six waves with not more than 3 bombs planted. First of all every game will be a bit different so you might want to consider adjusting your playstyle and adapt. When you first touch down you will need to clear the bunker at hardpoint A before the first wave starts.
bear in mind any bomb planted during that warm up round DOES NOT count towards the total of bombs allowed to be planted. the bombs planted when you are clearing the bunker at the begingin DOES NOT count. The count starts from wave 1.
Your weapon of choice: it's a matter of preference, I used the lmg for its high ammo capacity. for my secondary weapon i just chose one with faster reload time.
Class: You should definitely both pick assault. armor plates make all the difference. My friend switches a lot, but I prefer assault. just don't forget to resupply on armor plates you and your teammate.
Shop: save your money for waves 4-5-6. Most important items are the sentry turret, self revive, reinforcement and maybe a couple of cruise missiles for wave 6.
The trick:The trick I did that made the mission a lot easier was blocking hardpoint A with cars scattered around the playable area to alleviate the pressure off point A and give me breathing room to clear Hardpoint B, while my teammate took care of C.
make sure to block them in a way they can't get around it by dropping from above the entrance. just make sure to have A set up before the end of wave 5. Usually I keep the helicopter hovering in wave 2 and not destroy it until I move a couple of cars. or leave one straggler AI to buy some time.
the entrance in A with the long corridor in the back, you need to get the whole car in and park it in an angel. if you just block the stairs outside the AI will somehow figure it out and drop down. It happened to me.
I left one entrance accessible for us in case we needed a quick way out, . but I made sure that all enemy AI were funneled in a one line of sight for my turrets. That way I can be at point B and ready to provide assistance at C. When I notice A being overwhelmed, the blocked entrance and turrets will definitely buy me time to get there before they settle in and plant. Also with a cruise missile being ready to go I can be away from A and just call in a missile to destroy the AI already gathered in one place thanks to the cars I placed.
check my video where I show How I placed the cars to block A: