context: At the end of 1882, Nietzsche traveled to Rome, where he met Lou Salome (1861-1937), which left a significant mark in his life. From the first seconds, Nietzsche was subdued by her flexible mind and incredible charm. He found a sensitive listener in her, she, in turn, was shocked by the ardor of his thoughts. He twice proposed to her, but she refused, offering her friendship in return. After some time, together with their mutual acquaintance Paul Re, they organize a kind of union, living under one roof and discussing the philosophical ideas. But six months later he was destined to break up: Elizabeth, Nietzsche’s sister, was unhappy with Lou’s influence on her brother and resolved this problem in her own way by writing a rude letter to her. As a result of the ensuing quarrel, Nietzsche and Salome parted forever. Soon, Nietzsche will write the first part of his key work "So Said Zarathustra", which guesses the influence of Lou and her "ideal friendship." In April 1884, the second and third parts of the book were published at the same time, and in 1885 Nietzsche published the fourth and last in his own money in the amount of only 40 copies and distributed some of them to his close friends, including, for example, Helene von Druskovits.
question: What was the key product of Nietzsche called?
answers.text: "So Said Zarathustra"