Answer
$$h^{\prime}(x) =4f^{\prime}(g(\sin 4 x)) g^{\prime}(\sin 4 x)(\cos 4 x) $$
Work Step by Step
Given
$$h(x)=f(g(\sin 4x)) $$
Then
\begin{align*}
h^{\prime}(x)&=f^{\prime}(g(\sin 4 x)) \cdot \frac{d}{d x}(g(\sin 4 x))\\
&=f^{\prime}(g(\sin 4 x)) \cdot g^{\prime}(\sin 4 x) \cdot \frac{d}{d x}(\sin 4 x)\\
&=f^{\prime}(g(\sin 4 x)) g^{\prime}(\sin 4 x)(\cos 4 x)(4)
\end{align*}