Factor completely z^4-y^4?

Question

z^4-y^4

its a bonus question on my algebra test and i need it by tomorrow

Answer 1

z^4-y^4

(z^2-y^2)(z^2+y^2)

(z-y)(z+y)(z^2+y^2) --------------final answer

Answer 2

(z^2 - y^2)(z^2 + y^2)

and that factorises some more:

(z - y)(z+y)(z^2 + y^2)

Answer 3

nvm i messed up