The deity at the center of the pediment on the temple of zeus at olympia (4.2.1), who brings order to the scene, is

I believe the correct answer is: Apollo.
 
The pediments of the Temple of Zeus at Olympia are some of the best surviving examples of early Classical Greek sculpture which were completed in 460 BCE. On the west pediment ('centauromachy' – battle between centaurs and the Lapiths) Zeus stands in the center on the east and Apollo on the west. But, Apollo is the deity who brings order to the scene as he is a deity promising to restore order as the deity of rationality and self-control.