Is it permissible to perform the Witr prayer and the numerical dhikr before the adhan of Fajr, and postpone the rest of the dhikr until after Fajr?

What you do of dhikr (remembrance of God) and du'a (supplication) during the time of dawn (sahar) is permissible; in fact, it is among the best and most excellent deeds, based on the Almighty's saying: "And those who seek forgiveness in the dawns," and according to the Prophet's (peace be upon him) hadith: "Our Lord, the Blessed and Exalted, descends every night to the lowest heaven when only the last third of the night remains, and He says: 'Is there any supplicant that I may answer him? Is there any asker that I may give him? Is there any seeker of forgiveness that I may forgive him?'" Delaying the morning adhkar until after the Fajr prayer is also permissible, and it is one of their best times, extending from the true dawn until sunrise.