# Who is Abimelek, and who is Shechem, that we should serve him?

"We should not serve Abimelek, that is, Shechem!" 

# Is he not the son of Jerub-Baal? Is Zebul not his overseer?

"He is just the son of Jerub-Baal, and Zebul is just his overseer." 

# overseer

Zebul oversaw Abimelek's slaves, servants, and laborers.

# Zebul

This is the name of a man.

# Serve the men of Hamor, Shechem's father

Gaal means the people of Shechem should serve those who descended from Hamor, that is, those who are truly Canaanites, and not serve someone whose father was an Israelite.