Es sei ${\displaystyle {}R}$ ein kommutativer Ring und seien ${\displaystyle {}x,y}$ und ${\displaystyle {}z}$ Elemente in ${\displaystyle {}R}$. Berechne

${\displaystyle {\left(2x^{3}-xy^{2}z-4x^{2}y^{2}\right)}{\left(-2x^{3}-z-xyz\right)}-x^{2}{\left(4-3y-5xy^{5}z\right)}.}$