TeX source:
\begin{array}{rcl} f'_{yy}(x,y,z) &=& \dfrac{140\pi xy^3\cdot\cos\left(7y^5\right) + 35\pi xy^4\left(-\sin\left(7x^5\right)\right)\cdot 35y^4}{e^{10xz+1}} \\\\&=& \dfrac{140\pi xy^3\cos\left(7y^5\right)-1.225\pi xy^8\sin\left(7x^5\right)}{e^{10xz+1}}\end{array}