That's a pretty good point but I like how Zenii soundsIf there are other names in the series that is in the theme of celestial bodies like "Jupiter" then Zenith should be the actual translation since it is a term used in relation with celestial bodies.
It has a hidden meaning to the series as the MC would be at the highest point of magic as per the meaning of the word itself.
But you do you. Translation is still an art form after all. You can make some artistic changes.