there was a similar question but sometimes you cite theorems just by of authors, e.g. you don't say by the Hopkins-Levitzky theorem we conclude but you just say it follows from Hopkins-Levitzky.
and in this situation, I am quite confused. My instinct tells me to omit the definite article, but my instincts are often wrong (in my native language we don't have articles). I am still citing the same theorem (just omitting to say theorem ) and it is a unique theorem.
Of course, I can avoid this issue by calling it always the full name but sometimes this does not feel natural.
EDIT: I am using Hopkins-Levitzky as an example because in this case, it is obvious that I am not meaning them as a person(s) but as a shorthand for their theorem. But this situation, I think, applies in other cases, when from context everyone knows I mean the theorem itself and not mathematician. For example, if you cite some Eklof's theorem in the text, name it as Eklof's and then you refer to it only as "Eklof".