Complex sentence: One day, his old friend Cézanne, still poor and unknown, visits him before leaving the city, and tells Zola that with his success he has become complacent, a far cry from the zealous reformer of his youth.
Split into simpler sentences: One day, his old friend Cézanne, still poor and unknown, visits him before leaving the city. He tells Zola that he has become complacent, a far cry from the zealous reformer of his youth.