Keep the distance and make sure you shoot one of them until it charges in
Wait until he's close enough (notice the slow motion)
Dodge to a side using SHIFT + LEFT/RIGHT and DON'T shoot
If you did it properly Lara will dodge and a target will form on the head of the centaur
When the target is red, SHOOT
The centaur will be stunned and you'll have a few second for the next step
Turn towards the centaur and use Q to grab the shield, then quickly use E to disarm him
Repeat this for the second centaur as well
When both of them are disarmed, shoot one again until he is angry again, but this time stay close to one of the fallen shields
This time, he'll try to use the stoning gaze, so when he tries to do this, quickly go to the shield and use E to hold it AND face it towards him
He should be stoned for a few seconds
Shoot him until he crumbles into pieces, use the dual 50 caliber pistols since they do much more damage
Repeat this for the second centaur
And that's pretty much it.