also = thus
sprach = spoke
Zarathustra = the persons name
The official translation is "Thus spoke Zarathustra", the normal phrase would be "Zarathustra said...".
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Also sprach Zarathustra (1883-1885) is a book by Friedrich Nietzsche. The title is often translated as Thus spake Zarathustra. Spake is an archaic form of spoke.