When, how, and by whom was the Holy Quran divided into thirty parts, and each part into two hizbs, and each hizb into four quarters, and on what basis was this division made?

The well-known practice among the Companions in dividing the Qur’an into sections (hizb) was based on surahs, not on verses or letters. They used to make it seven sections. As for the aforementioned division, it began in Iraq during the time of Al-Hajjaj ibn Yusuf, and in it, the number of letters was taken into consideration.