Complex sentence: As an architect, having been trained as a sculptor and stonemason in the design of moldings, he reached a remarkable equilibrium of proportions, and was among the first to diffuse the "severe" style initiated by Antonio da Sangallo the Younger.
Split into simpler sentences: As an architect, his former education as a sculptor and stonemason in the design of moldings allowed him to reach a remarkable equilibrium of proportions. Moreover, Mangone was among the first to spread the "severe" style initiated by Antonio da Sangallo the Younger.