Complex sentence: The St. Vincent panels were no longer merely a masterful painting, any more than the "Os Lusíadas" was merely a wonderful poem--they were national epics, glorifying a nation and its history.
Split into simpler sentences: The St. Vincent panels were no longer merely a masterful painting, any more than the "Os Lusíadas" was merely a wonderful poem. They were national epics, glorifying a nation and all its history.