Endings with more than two major pieces usually proceed to checkmate in the same way as those with just two major pieces.
Of course a tremendous advance in material allows for shortcuts.
This denies the fifth rank to Black. He'll have to chose between 4th and 6th rank, but both are equally doomed.
The king tries to approach the rook (hopelessly).
This cuts off the third rank. The black king is fixed on the fourth rank and one move away from being mated.
The king, although he knows that death is imminent, continues to approach the rooks.
Checkmate! The Black king cannot stay on the fourth rank because of the rook on c4. He can't flee to the fifth rank because of the rook on a5. And he can't flee to the third rank because of the rook on c4. My, that was quick, wasn't it?