Complex sentence: After Mauro's death, he tried briefly to work on his own but eventually accepted a position in Udine, collaborating with another Mauro, Antonio, to do the frescoes at a theater being decorated by the painter Giambattista Canal, whose eyesight was failing.
Split into simpler sentences: After Mauro's death, he tried briefly to work on his own but eventually accepted a position in Udine. He collaborated with another Mauro-Antonio, to do the frescoes at a theater that were originally decorated by the painter Giambattista Canal, whose eyesight was failing.