Complex sentence: The "Maître d'oeuvres" were Pierre le Tirrant and Roland le Besque, the carpentry was by Yvon Cogan and Pierre Nicholay and the granite used came from either the Île Grande or from Pluzunet.
Split into simpler sentences: The "Maître d'oeuvres" were Pierre le Tirrant and Roland le Besque. The carpentry by Yvon Cogan and Pierre Nicholay and the granite used came from either the Île Grande or from Pluzunet.