The roots of polynomial $ p(z) $ are:
$$ \begin{aligned}z_1 &= 1.7257\\[1 em]z_2 &= 2.7994\\[1 em]z_3 &= -0.7625+1.2201i\\[1 em]z_4 &= -0.7625-1.2201i \end{aligned} $$Step 1:
Combine like terms:
$$ z^4 \color{blue}{-2z^3} \color{blue}{-z^3} -2z+10 = z^4 \color{blue}{-3z^3} -2z+10 $$Step 2:
Polynomial $ z^4-3z^3-2z+10 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.