Answer
$\dfrac{y^6}{z^{12}}$
Work Step by Step
Using the laws of exponents, the given expression, $
(y^{-2}z^4)^{-3}
,$ is equivalent to
\begin{array}{l}\require{cancel}
y^{-2(-3)}z^{4(-3)}
\\\\=
y^{6}z^{-12}
\\\\=
\dfrac{y^6}{z^{12}}
.\end{array}