Factorise over C if P(-i)=0

For all the book's questions so far we were told to find one factor after finding a root, then use long division to find the next factor and so on. But I am not sure where to start here because of the "i"s in the polynomial.

So all I know so far is that (Z-(-i)) = (z+i) is a factor. But I don't think I will be able to divide 9z^3+(9i-12)z^2+(5-12i)z+5i by (z+i)

Thank you