Question: Problem with transformations of complex numbers

Please help me with transformation of the following expression:

> z:=abs(a)^2*b+abs(a)^2*c*conjugate(a);

where I want to derive

a*(conjugate(a)*b+conjugate(a)^2*c)

I try the following:

> z:=collect(z,a);

However it does't transformate z in any way.

 

In other words if I have
>z:=a*conjugate(a);

>z:=simplify(z);

I derive z=|a|^2. How to decompose z back into a*conjugate(a)?

 

Thank you.

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