$${ \left(3 { x }^{ 2 } -2ax+3 { a }^{ 2 } \right) }^{ 3 }$$
$27x^{6}-54ax^{5}+117a^{2}x^{4}+117x^{2}a^{4}-54xa^{5}-116\left(ax\right)^{3}+27a^{6}$
$\left(3x^{2}-2ax+3a^{2}\right)^{3}$
