Complex sentence: The vast majority of western Ukraine's intelligentsia and clergy were members of UNDO, and they controlled many of the region's Ukrainian financial, cooperative, and cultural institutions, including the principal western Ukrainian newspaper Dilo.
Split into simpler sentences: The vast majority of western Ukraine's intelligentsia and clergy were members of UNDO. UNDO's members controlled many of the region's Ukrainian financial, cooperative, and cultural institutions, including the principal western Ukrainian newspaper Dilo.