$\frac{{12}^8\cdot 4^8}{9^4\cdot {16}^4}=\frac{{\left(12\cdot 4\right)}^8}{{\left(3^2\right)}^4\cdot {\left(4^2\right)}^4}=\frac{{\left(12\cdot 4\right)}^8}{3^8\cdot 4^8}={\left(\frac{12\cdot 4}{3\cdot 4}\right)}^8={\left(\frac{12}{3}\right)}^8=4^8={\left(4^2\right)}^4={16}^4={\left({16}^2\right)}^2={256}^2=65536$