Answer
$12z^{4}-14z^{3}+19z^{2}-22z+8$
Work Step by Step
$ \begin{array}{lllllll}
& & & 4z^{3} & -2z^{2} & +5z & -4\\
& & & & & 3z & -2\\
& & & & -- & -- & --\\
& & & -8z^{3} & +4z^{2} & -10z & +8\\
& & 12z^{4} & -6z^{3} & +15z^{2} & -12z & \\
\hline & & & & & & \\
& & 12z^{4} & -14z^{3} & +19z^{2} & -22z & +8
\end{array} \qquad \begin{array}{l}
.\\
.\\
.\\
\leftarrow-2(4z^{3}-2z^{2}+5z-4)\\
\leftarrow 3z(4z^{3}-2z^{2}+5z-4)\\
\\
\leftarrow\text{combine }
\end{array}$