Be sure to save before trying, so if you die, just reload the previous save.
Two Centaurs will run in circles around Lara and throw fireballs at her. Just keep moving, so the fireballs they throw don't hit you.
Lock on to one of the Centaurs with the left-trigger and shoot. When it's rage bar is full, the Centaur will perform it's stone gaze attack (a green flash). When this begins let go of the left trigger to put down the guns. If not, then you will be turned to stone. If you were changed to stone, move the
left analog from left to right to break out. One of the Centaurs will then run toward you and try to kick you, which shatters you (one hit kill).
Shoot the Centaurs again to fill the rage bar again. But this time, it will run toward you and try to hit you. When the screen distorts, press B and move to a side then shoot it when the targeting markers align and turn red. The Centaur will then be stunned afterward. Press X to grapple the ring on the Centaur's shield, then press Y to pull the shield out. Do this again for the other Centaur.
Once you have taken both shields, shoot one until the rage bar is filled, then it will perform it's stone gaze. Quickly run over to one of the shields and press Y to pick it up, face the Centaur that is stone gazing to turn that Centaur into stone. Shoot the Centaur while it is frozen to damage and kill it. Keep repeating this process until both are dead.
Credit to klioki on video.