Komentaryo sa Zacarias 14:6: Rashi, Metzudat Zion, Radak & Tze'enah Ure'enah

there shall be no light, only disappearing light and thick darkness Jonathan renders. There shall not be light, only light that passes away, and thickness, i.e., there shall not be splendrous light, only יְקָרוֹת and קִפָּאוֹן shall [there] be. יְקָרוֹת An expression similar to (Ps. 37:20), “like the disappearing light over the plains.” Like a sort of light that appears in the morning over the mountains and disappears little by little.

Light of yeqarot. Clear/bright light as in (Job 31:26) "or the moon walking yaqar (in brightness/splendor).

And it shall come to pass on that day - on the day that he mentioned that there would be the sign, this is the matter, that there will not be light of yeqarot nor of qippa'on, and the interpretation by way of analogy is that the light of day will not be bright, which is the light of yeqarot, as in "the moon walks yaqar (in brightness)" (Job 31:26), and neither [will there be] light of qippa'on, which is frozen and thick, which is like darkness. And the interpretation is that that day will not be neither all like light nor all like darkness, meaning neither comfortable nor troubling, but rather both of them will be in it. And likewise he (Zechariah) says after it (verse 7)"not day and not night." And Jonathan translated, "there will not be light, but rather passing light and ice/thickness/congealment"

וְקִפָּאוֹן Congealed and dark and thick, like ice that is congealed and frozen, as in (Job 10: 10), “And like cheese You curdled me.”