Tt has been clarified by the interpreters in different Tafsirs that Qur’an is revealed in two different formats:
1. Instant format: Nuzul Daf’i
2. Gradual format: Nuzul Tadriji The first format was revealed in the Night of Powers in the holy month of Ramadan in which Qur’anic values and principles were revealed on the heart of the prophet. The verb “Inzal” indicates such type of revelation in different verses. Whereas the verse by verse Qur’an which the second format suggests was revealed in 23 years of the life of prophet. The verb “Tanzil” refers to such type of revelation in Qur’an. So the verse you quoted indicates the first type of revelation.
Shaykh Kumail Rajani