Some tips on technique from Grand Master kdog:
Just put the spanner down onto the metal collar and bang away, the plastic nut will come with it - broken or not it gets discarded anyhow as the new tubnut has it integrated
And a Tip de Grace from Grand Master Reg:
just for the record ...
Perhaps I could keep banging away. spent an hour beating the spanner with a hammer yesterday and it would not budge.
these later model Maytags have "normal" right-hand threads..