\(=\left(10-4\sqrt{3}\right)\left(7+4\sqrt{3}\right)-8\cdot\sqrt{20+2\cdot\left(3\sqrt{3}+4\right)}\)
\(=70+40\sqrt{3}-28\sqrt{3}-48-8\cdot\sqrt{28+6\sqrt{3}}\)
\(=22+12\sqrt{3}-8\left(3\sqrt{3}+1\right)\)
\(=22+12\sqrt{3}-24\sqrt{3}-8=14-12\sqrt{3}\)