Solution (source code)

= Solution

Taking each <partial derivative> of the <scalar potential> gives
$$
\boxed{\mathbf F=\left(\cos(y^5)\sinh z,
-5xy^4\sin(y^5)\sinh z,
x\cos(y^5)\cosh z\right)}.
$$
The factor $5y^4$ in the middle component comes from the <chain rule>. The potential is smooth, so the <curl of a gradient> identity gives $\boxed{\nabla\times\mathbf F=\mathbf0}$.