"主神朱庇特的" can be translated as "of the supreme god Jupiter" or more contextually appropriately as "pertaining to Jupiter, the king of the gods" (depending on the specific context, but the former is a more direct literal translation).
In simpler or more common expressions, you might just say "Jupiter's" when referring to something belonging to or associated with Jupiter, the Roman god (equivalent to Zeus in Greek mythology). For example:
"Jupiter's power" (朱庇特的力量)
"The myths of Jupiter" (朱庇特的神话)
If you specifically want to emphasize his status as the chief or supreme god, you could use "of Jupiter, the supreme deity" or similar phrases, but "of the supreme god Jupiter" is already a clear and accurate translation.