Maple simplify - expression of vars through other vars

Question

I have a string

W := lx1sx1ph11alpha1ph12beta2-lx1sx1ph12alpha2ph11beta1+lx2sx2ph11alpha1ph12beta2-lx2sx2ph12alpha2ph11beta1

I want use the simlify with the condition to remove sx1 and sx2:

Right := simplify(W, {sx1*alpha1 = .5*beta1, sx1*beta1 = .5*alpha1, sx2*alpha2 = .5*beta2, sx2*beta2 = .5*alpha2})

But, maple can't do it and gives me

Right := (1/2*(-lx1*ph11*ph12+lx2*ph11*ph12))*alpha2*alpha1+(1/2*(-4*lx2*ph11*ph12+4*lx1*ph11*ph12))*sx2*alpha2*sx1*alpha1

How can I improve it and solve?

Answer 1

W := lx1*sx1*ph11*alpha1*ph12*beta2 - lx1*sx1*ph12*alpha2*ph11*beta1
     + lx2*sx2*ph11*alpha1*ph12*beta2 - lx2*sx2*ph12*alpha2*ph11*beta1:

simplify(simplify(W, {sx1*alpha1 = 1/2*beta1, sx2*alpha2 = 1/2*beta2}),
         {sx1*beta1 = 1/2*alpha1, sx2*beta2 = 1/2*alpha2});

    1/2*ph11*ph12*(-alpha1*alpha2+beta1*beta2)*(lx1-lx2)