Use the sniper rifle (#147) and wait until Zakhaev gets there (#148). When MacMillian tells you, shoot him, but do take the wind into consideration. Just watch the flag on the car. If its flickering too much, move the crosshair to the left or to the right (depending on the direction of the wind ).
When you shoot at Zakhaev, he will lost his arm but according to MacMillian that's enough. Then shoot once more, this time at the pilot sitting in the helicopter (#149). It will get pretty hot then, and you will have to run. Follow the captain (#150), grab the line and go down.
Enemies will show up. Kill some of them and when MacMillian says so, start running. You will get to a building (#151), in which you will be able to hide for a while.
Wait for MacMillian to open the door and then go straight ahead. After a couple of seconds, wild dog will attack you. Kill it and keep moving. Soon more enemies will show up. To make it easier for yourself, plant some mines by the front door. Before you leave the building (#152) pick up the enemy's weapon - it will be useful soon.
Kill the next soldiers that will attack you and then shoot at the helicopter (#153). It will crash and pin down the captain(#154). That means trouble.
Form this point you have to carry your commander, and that means you will be completely defenceless. MacMillian will help you with killing enemies but first you will have to lay him on the ground. Soon you will have a chance to try that method out as enemies will show up. The second time will be in a small park (#155), enemies will attack there again. But this time there will be more enemies and they will attack from many different directions.
When you deal with them get the captain and walk into the building (#156). Get on the first floor. When you see a dog, kill it and then keep moving.
After some time you will get to the ferris wheel (#157). This is the place of the final battle. Kill the soldiers patrolling the area and put MacMillian where he tells you. He will shoot at the enemies that will show up soon. Use the time you have to plant some mines. It's good to place them next to the cars as soldiers will hide behind them (#158). Plant some C4 as well, you will be able to detonate them later.
To finish this mission you will have to supress all the attacks until a helicopter comes to pick you up. This task won't be easy as terrorists will be coming in great numbers. I suggest staying close to MacMillian and eliminating coming enemies with the sniper rifle. If anyone tries to get to you from the other side of the ferris wheel (#159), use the weapon you got before.
When the helicopter is finally there, pick up MacMillian and get him in it. (#160). This mission is over.