Then by those groups that recites Quran.
The reciters of the messages.
and those who recite the Remembranc
And those who recite the Reminder
So the reading/reciting/following, mentioning/remembering
And by the angles who bring the verses of Qur’an down to mankind
And by oath of the groups that read the Qur’an
And those who recite the Reminder - the Qur'an
Then by those parties that remember Allah (or) recite (the Holy Qur’an)
And those who recite and follow the Reminder (- the Qur'an)
By those (angels) who bring the Book and the Quran from Allah to mankind (Tafsir Ibn Katheer)