\[\frac{56x^{3}y^{4}}{z^{5}} \cdot \left( - \frac{z^{4}}{16x^{2}y^{6}} \right) =\]
\[= - \frac{56x^{7}y^{4}z^{4}}{z^{5} \cdot 16x^{2}y^{12}} = - \frac{7x}{2zy²}\]