Answer
$$ z_x=4x^3y+y^{-2},\quad z_y=x^4-2xy^{-3}.$$
Work Step by Step
Recall that $(x^n)'=nx^{n-1}$
Since $ z=x^4y+xy^{-2}$, then we have
$$ z_x=4x^3y+y^{-2},\quad z_y=x^4-2xy^{-3}.$$
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