X1=K1*(1-C)(1-D)(1-C*K/q)(1-D*K/q)(1-G/q)(1-H/q)+
  K2*(1-C*K)(1-C*K/q)(1-D/q)(1-D)(1-G/q)(1-H/q)+
  K3*(1-D*K)(1-D*K/q)(1-C/q)(1-C)(1-G/q)(1-H/q)+
  K4*(1-C/q)(1-C)(1-D/q)(1-D)(1-G*K/q)(1-H*K/q);
X1=Table[Coefficient[X1,K,i]==0, {i,0,2}];
X1=Solve[X1,{K1,K2,K3,K4}];
X1={K1->Factor[K1/.X1[[1]]],K2->Factor[K2/.X1[[1]]],K3->Factor[K3/.X1[[1]]],K4->Factor[K4/.X1[[1]]]}

{K1->Factor[X1[[1,2]]/X1[[4,2]]],K2->Factor[X1[[2,2]]/X1[[4,2]]],K3->Factor[X1[[3,2]]/X1[[4,2]]],K4->Factor[X1[[4,2]]/X1[[4,2]]]}