Find all values of the real number \(a\) so that the four complex roots of\(z^4 - 6z^3 + 11az^2 - 3(2a^2 + 3a - 3) z + 1 = 0\) form the vertices of a parallelogram in the complex plane. Enter all the values of \(a\), separated by commas.
The only one for a that I found is 3.
+483 
