If 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...
Prediction:
His crush will become his love rival
The two engaged becomes love rivals
The other dude becomes a love rival
I know it sounds confusing but it will, if I'm right (probably not)