First, factor the expression as:
#(6 * 2 * c * c^2)/(3 * 7 * b) * (2 * 7 * b * b)/(6 * c)#
Next, cancel common terms in the numerator and denominator:
#(color(red)(cancel(color(black)(6))) * 2 * color(blue)(cancel(color(black)(c))) * c^2)/(3 * color(green)(cancel(color(black)(7))) * color(purple)(cancel(color(black)(b)))) * (2 * color(green)(cancel(color(black)(7))) * color(purple)(cancel(color(black)(b))) * b)/(color(red)(cancel(color(black)(6))) * color(blue)(cancel(color(black)(c)))) =>#
#(2 * c^2)/3 * (2 * b)/1 =>#
#(2 * c^2 * 2 * b)/(3 * 1) =>#
#(4bc^2)/3#