Moshe is blessing the tribes before they enter into the Land of Israel without him. In 33:18 it says, "שמח זבלון בצאתך ויששכר באהליך" - Rejoice, Zebulun, in your going out, and, Issachar, in your tents.
Rashi says that Zevulun is mentioned first because he supported Yissachar, ergo Yissachar's Torah was only via the merit of Zevulun.
Our society has become one in which we do not give the due respect to those who support Torah. We consider them to be necessary, but on a lower level. Those learnign Torah, we think, are doing a higher calling and are the pinnacle of Judaism. Those who work are lower class of sorts.
The Torah says otherwise. The Torah puts Zevulun, the merchant, before Yissachar. The Torah says that those who support Torah are at least of equal calling, if not greater. Zevulun was mentioned first because he enables Yissachar to learn.