Converting to and from partial fractions

This is an example of where Axiom's handling of domains fries my limited
brain.

ex:=z/(z-1)+2*z/(z-3)

(Result is returned as a single polynomial fraction.)

Now, what I want to do is to break this single fraction up into its original
components.  The canonical way to do this (for my purposes), is to divide
the fraction by z, form partial fractions, and multiply through by z.  Here
goes:

exf:=partialFraction(ex/z::FRAC POLY INT,z)$PFRPAC(INT)

Now, because the result is returned as a partial fraction,if I try

nthFractionalTerm(exf,1)*z

I don't get 2*z/(z-3), but 2+6/(z-3).  So I need to remove this term from
its partialFraction domain.

But none of nthFractionalTerm(exf,1)::FRAC POLY INT,
nthFractionalTerm(exf,1)::EXPR INT seem to work.

Any ideas?

Thanks,
Alasdair

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