These two were the two youngest sons of Leah and I imagine they probably hung out a lot together, so they ended up being very similar types of people and therefore treated together. Now, Jacob separates them into two separate prophecies while Moses puts them into one blessing. What Jacob emphasizes is Zebulun's coastal seafaring maritime setting. They are all about the ocean. On the other hand, he emphasized Issachar's strength and work ethic. He is a strong donkey, he is a servant, he does the work.
