This is the 7719th most frequent Russian word.
зенитом
The Russian word "зенитом" means "zenith" in the instrumental case, referring to the highest point or peak.
In this sentence, 'зенитом' is used to describe the position of the sun being at its highest point in the sky.
Солнце находилось в зените.
The sun was at its zenith.
Here, 'зенитом' metaphorically signifies the peak or highest point of someone's career.
Его карьера уже прошла свой зенит.
His career has already passed its zenith.
'зенитом' refers to the peak period of a summer day, suggesting maximum heat or intensity.