Find the modulus and argument of the complex numbers $\displaystyle z_1 , z_2 ,z_3$ if $\displaystyle z_1=1-i$ ,

$\displaystyle z_2=z_1^3$ and $\displaystyle z_3=\frac{\sqrt3-i}{\sqrt3+i}$

I just couldn't understand this part :$\displaystyle z_2=z_1^3$ .. what does it mean ?