hello, i have to determine the complex zero values of the function z^5+2z^3+z

ok here my try:

z (z^4+2z^2+1) = 0 => gives first zero pt. at 0

now substitution z^4 =u^2 and z^2 = u

now with pq formula i get this: -1+- 0

but what now ??

thanks in advance !