Passage
And there shall be one day, which is known to the Lord, not day nor night: and in the time of the evening there shall be light:
And there shall be one day, which is known to the Lord, not day nor night: and in the time of the evening there shall be light:
Zechariah 14:5 And you shall flee to the valley of those mountains, for the valley of the mountains shall be joined even to the next, and you shall flee as you fled from the face of the earthquake in the days of Ozias king of Juda: and the Lord my God shall come, and all the saints with him.
Zechariah 14:6 And it shall come to pass in that day, that there shall be no light, but cold and frost.
Zechariah 14:7 And there shall be one day, which is known to the Lord, not day nor night: and in the time of the evening there shall be light:
Zechariah 14:8 And it shall come to pass in that day, that living waters shall go out from Jerusalem: half of them to the east sea, and half of them to the last sea: they shall be in summer and in winter.
Zechariah 14:9 And the Lord shall be king over all the earth: in that day there shall be one Lord, and his name shall be one.
The verse centers on "light", "shall", "known", "lord", "night", "time", and "evening". It is saying that the verse draws attention to "light" and "shall", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 6's "And it shall come to pass in..." into verse 8's "And it shall come to pass in...", so "light" and "shall" belong inside that flow. In Zechariah context, the local focus is covenant, worship, and faithfulness.
A plain takeaway is to answer the verse's own emphasis on "light" and "shall" with trust shaped by these words, not by a vague optimism outside the passage.