The Republican Tax Bill needs to be written into regulations. Normally, that does not happen overnight, UNLESS, Mnuchin already has them written and the law was then written to fit the regulations.
That is the only way a substantial tax law can go into effect January 1, 2018 or sooner.
If there are regulations waiting for a law, the Democrats need to investigate that fact.
In regard to Director Mueller; there is no grounds for the political complaints of Republicans.
The GOP's complaints are laying down the reason for Trump's pardons of his family and allies. It has nothing to do with Mueller. Trump even said he is not removing Mueller from the investigation. Trump is demanding his party lay down the ground cover for his pardons.