\(\dfrac{4^6\cdot9^3+6^9\cdot120}{8^4\cdot3^{12}\cdot6^{11}}=\dfrac{2^{12}\cdot3^6+2^9\cdot2^3\cdot3^9\cdot3\cdot5}{2^{12}\cdot3^{23}\cdot2^{11}}\)
\(=\dfrac{2^{12}\cdot3^6+2^{12}\cdot3^{10}\cdot5}{2^{23}\cdot3^{23}}\)
\(=\dfrac{2^{12}\cdot3^6\left(1+3^4\cdot5\right)}{2^{23}\cdot3^{23}}=\dfrac{1}{2^{11}}\cdot\dfrac{1}{3^{17}}\cdot406\)
\(=\dfrac{203}{2^{10}\cdot3^{17}}\)