Zarda and Kodux is the second last encounter in the Temple of Kor-Sha.
Before engaging make sure you have cleared all the wandering adds. Make sure to kill the assassins that are hidden in the waterfalls. And finally make sure you have killed the golems in each room of the names.
Split your raid into two groups of even dps. You will want to kill these separately at an equivalent rate. While killing the two names have the two tanks call the hit points at each 10% so you know they are going down at about the same rate. If they aren't call a dps class to move over to the other mob. If they get past 30% difference they will start to AOE hard which will not be survivable for an under-geared raid force.
The location to fight them is just up the stairs from the waterfall room slightly into the halls, don't fight them in their rooms. They will port people into the middle of the waterfall room so having the tanks nearby to taunt their mob without going anywhere is very useful. There is also edges by the doorways to the waterfall room the tank can use to put his back into. This will help a lot with the knock back from the mobs.
The two names will target two people, port them to the middle room, and then go running for them. At this point the two tanks must call who got ported so they can run to the tank who called them. The tank will know because they have the mob targeted and can see who its new implied target is. The tank will tell you to go north or east depending where they are, don't move until a tank tells you which side to come to. Once the tank has agro back on the mob then head back to the group you are supposed to be with.
Occasionally a tank will get ported to the middle room. The tank must wait there for the other tank to pull his mob off him. If both mobs are together they will power drain who they are targeting. Once the tank has pulled his mob off the other tank (or coercer thought snap, dirge magnetic note, guardian recapture) the tank can go back to his spot. Or if his own mob ported him to the middle then the other tank can say "you are safe" and the tank that got ported can go back to his hall with his mob. Your monk can also help out by pulling the mob back to the correct room.
Keep comms quiet and just listen for the tanks calling you to their hall and no one will die.