Today, the Supreme Court ruled that Slaughter gets slaughtered, but that Cook won't get cooked! In Trump v. Slaughter, a 6-3 Court divided along ideological lines ruled that the president generally has absolute power to remove the heads of executive branch agencies, even when Congress has enacted laws limiting that authority. At least as a general rule, those laws are - according to the Court - unconstitutional infringements on the president's executive power. Thus, Trump can give Democratic Federal Trade Commission member Rebecca Slaughter the axe.
By contrast, in Trump v. Cook, a 5-4 majority (including two of the justices who were also in the majority in Slaughter), ruled that Trump does not have unlimited power to fire members of the Federal Reserve Board. The Court ruled that the law allowing him to remove them only "for cause" is constitutional, and that "for cause" is a fairly high standard, compatible with maintaining the Fed's "independence." Moreover, if the president tries to fire board members for cause, he has to give them substantial due process. This doesn't definitively save Federal Reserve Board of Governors member Lisa Cook's job (Trump claims he can fire her due to accusations of mortgage fraud). But it certainly gives her and her colleagues strong protection against removal, and makes it clear the president cannot simply fire them whenever he wants.