Complex sentence: A Government of conciliation was formed, in which nationalists, socialists, communists and other republicans were present, not without tensions between them, which only used its powers in Vizcaya for several months until the fall of Bilbao.
Split into simpler sentences: A government of conciliation was formed with nationalists, socialists, communists, and other republicans, though not without tensions between them. The government was in power only in Vizcaya for several months until the fall of Bilbao.