It is theoretically possible to solve all quartics in terms of their coefficients,
using only the standard operations of arithmetic and roots with integer indices.
However, since it would be very laborious to do so in this case, here are
approximations for the 4 solutions, 2 real and two non-real.
z ≈ 1.38746303
z ≈ 11.74003348
z ≈ -1.063748255 + 1.228120608i
z ≈ -1.063748255 - 1.228120608i
Edwin