The above machlokes in regard to whether Zevulun receives reward or not if Yissachar ends up learning lo lishmah, is seemingly dependent on the two approaches we outlined above of how Yissachar‐Zevulun partnerships work. It’s clear from the Maharash Primo that he understands that Zevulun gets part of Yissachar’s reward (like R’ Moshe), therefore, it’s understandable that if Yissachar learns lo lishmah and therefore Yissachar has less reward, that Zevulun also gets less reward. אם המקור מושחת מאין ימצא מים במורד – “if the source is empty, where should he draw water from”.
Those who argue however, presumably understand that Zevulun doesn’t get his reward from Yissachar’s reward, rather, when Zevulun supports Torah he is doing a good thing, and Hashem rewards him for doing so. Therefore, it makes sense to say, that even if Yissachar ends up learning lo lishmah and receives no reward, it doesn’t take away Zevulun's reward. His reward was coming from Hashem, not from Yissachar. and since he did his best, he gets rewarded.
