At that time the Holy Roman Empire was at the zenith of its power.
at the zenith of
With the Sun at the zenith of your chart, your reputation will be on the rise, and your professional duties will go smoothly.
Angleton was at the zenith of his power, although the strain was beginning to tell on him.
With the attainment of maturity and at the zenith of biological existence, life's drive towards a goal in no wise halts.
be at the zenith of one's powers (fame)
He is at the zenith of his fortune.
