如图,在三棱台\({ABC}{-}A_{1}B_{1}C_{1}\)中,\(D{,}E\)分别是\({AB}{,}{AC}\)的中点,\({AB}{=}2A_{1}B_{1}{,}B_{1}E{⊥}\)平面\(ABC\),且\({∠}{ACB}{=}90^{{∘}}\).
\((1)\)求证:\(B_{1}C{/\!/}\)平面\(A_{1}{DE}\);
\((2)\)若\({AC}{=}3{BC}{=}6{,}{\triangle }AB_{1}C\)为等边三角形,求四棱锥\(A_{1}{-}B_{1}C_{1}{ED}\)的体积.