How to simplify with common expression

How to simplify further ?

How to try to pull comomon expression ?

syms c d x
assume(0 <=x & x <= pi/2 & d>0 & c <0)
f = (cos(x)^7*(2*c - 14*sin(x)^4 + 21*sin(x)^8 - 14*c^2*sin(x)^2 + 21*c^2*sin(x)^4 + c^2 - 14*c*sin(x)^2 - 14*c*sin(x)^4 + 42*c*sin(x)^6 + 1))/(16*d^5); 
simplify(f,'Steps',1000) %does not simplify further