\(V=-x^{2} y-x z^{3}+4.\)
The field \(\vec{E}=-\vec{\nabla} V=-\left(\frac{\partial V}{\partial x} \hat{i}+\frac{\partial V}{\partial y} \hat{j}+\frac{\partial V}{\partial z} \hat{k}\right)\)
\(\therefore \vec{E}=\hat{i}\left(2 x y+z^{3}\right)+\hat{j} x^{2}+\hat{k}\left(3 x z^{2}\right)\)