After you destroy the servers, head through the door that just unlocked and proceed into the corridor. Follow the path to get back to the stairs, which used to be closed up but will now be opened. Head up the stairs. You will reach a branching path ahead of you. You may either go to the left or the right, but it really doesn’t matter which one you choose. Just make sure that you have the backing of your squad behind you before you go charging off ahead, as there will be a big hoard of enemies ahead no matter which way you go.
The Spec Ops soldiers will have engaged the zombies in the corridors ahead, and all chaos will have broken loose in the mansion. Take this opportunity to strike while the Spec Ops soldiers don’t notice you there. You can take one of several approaches here. First off, you can aim to wound the Spec Ops soldiers, which will attract the hoards of zombies surrounding them to attack. At this point, you can back off from the fray and let the enemies take care of themselves until one side emerges the victor. Then, run in with your squad to mop up the victors. Alternately, you can toss a grenade of some sort into the middle of the chaos. A regular Frag Grenade will blow up a few enemies, while a Stun Grenade will give you a chance to unleash tons of ammo on the defenseless enemies ahead. If you are playing with an entirely human squad, it will also be feasible to send half of them around one side of the fork and the rest of you around the other side, effectively flanking the enemies. If you can’t kill all of the enemies before they start attacking you, take cover behind the discarded tables and boxes ahead of the Spec Ops soldiers, firing over cover to kill them.
After all of the enemies are dead, search the area for some Intel. There will be three pieces of Intel here in all, and they will be scattered about the area that the Spec Ops soldiers were defending in the center of the corridor. You will also be able to find alternate primary weapons littering the ground if you want to swap. Collect everything in the area, and then head to the double doors at the opposite side of the corridor to proceed into the next checkpoint.