There are a number of laws of indices going on here.
No law is more important than another. There are different ways of simplifying the expression.
#((2x^0xx 2x^3)/(xy^-4))^-3 " Look for the obvious laws first"#
=#((2color(red)(x^0)xx 2color(blue)(x^3))/(color(blue)(x)y^-4))^-3 " "color(red)(x^0=1), color(blue)(x^3/x = x^2)#
=#((2xxcolor(red)(1)xx2color(blue)(x^2))/y^-4)^(-3)#
=#(color(green)(2xx2x^2)/color(orange)(y^-4))^color(magenta)(-3)" "(a/b)^-m = (b/a)^(+m)#
=#(color(orange)(y^-4)/color(green)(2xx2x^2))^color(magenta)3#
=#(1/(2xx2x^2color(orange)(y^4)))^3" "color(orange)(x^-1 = 1/x)#
=#(1/(4x^2y^4))^color(red)3#
=#color(red)(1/(64x^6y^12))#
