you can get a result without $MU's by doing:
However, the result can be simplified by renaming
the indices ( c <--> d ), as you would do by hand.
That is what I have automatized (which was actually quite non-trivial, especially if there are higher tensors involced) in DiracSimplify (which is used in Calc), and the dummy indices generated are called $MU[...] .
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