The Messenger of Allah ﷺ restored his daughter Zaynab to Abul'As on the basis of the previous marriage, and he did not do anything afresh. Muhammad b. 'Amr said in his version: After six years. Al-Hasan b. 'Ali said: After two years.  

رَدَّ رَسُولُ اللَّهِ ﷺ ابْنَتَهُ زَيْنَبَ عَلَى أَبِي الْعَاصِي بِالنِّكَاحِ الأَوَّلِ لَمْ يُحْدِثْ شَيْئًا قَالَ مُحَمَّدُ بْنُ عَمْرٍو فِي حَدِيثِهِ بَعْدَ سِتِّ سِنِينَ وَقَالَ الْحَسَنُ بْنُ عَلِيٍّ بَعْدَ سَنَتَيْنِ  

the Messenger of Allah returned his daughter to Abul-'As bin Rabi' after two years, on the basis of the first marriage contract.  

أَنَّ رَسُولَ اللَّهِ ﷺ رَدَّ ابْنَتَهُ عَلَى أَبِي الْعَاصِ بْنِ الرَّبِيعِ بَعْدَ سَنَتَيْنِ بِنِكَاحِهَا الأَوَّلِ  

the Messenger of Allah, returned his daughter Zainab to Abul-As bin Rabi', with a new marriage contract.  

أَنَّ رَسُولَ اللَّهِ ﷺ رَدَّ ابْنَتَهُ زَيْنَبَ عَلَى أَبِي الْعَاصِ بْنِ الرَّبِيعِ بِنِكَاحٍ جَدِيدٍ  

[Machine] The Messenger of Allah ﷺ ordered his daughter Zainab to divorce her husband Abu Al-As ibn Al-Rabi'ah and her Islam had occurred six years before his. He did not initiate any witness or dowry.  

أَنَّ رَسُولَ اللهِ ﷺ رَدَّ ابْنَتَهُ زَيْنَبَ عَلَى أَبِي الْعَاصِ بْنِ الرَّبِيعِ وَكَانَ إِسْلامُهَا قَبْلَ إِسْلامِهِ بِسِتِّ سِنِينَ عَلَى النِّكَاحِ الْأَوَّلِ وَلَمْ يُحْدِثْ شَهَادَةً وَلا صَدَاقًا  

[Machine] The Messenger of Allah, ﷺ , annulled the marriage of his daughter Zainab to her husband Abu Al-As ibn Al-Rabi' and did not change anything.  

رَدَّ رَسُولُ اللهِ ﷺ زَيْنَبَ ابْنَتَهُ عَلَى زَوْجِهَا أَبِي الْعَاصِ بْنِ الرَّبِيعِ بِالنِّكَاحِ الْأَوَّلِ وَلَمْ يُحْدِثْ شَيْئًا  

the Messenger of Allah returned his daughter to Abul-'As bin Rabi' after two years, on the basis of the first marriage contract. (Using translation from Ibn Mājah 2009)   

أَنَّ رَسُولَ اللهِ ﷺ رَدَّ ابْنَتَهُ زَيْنَبَ عَلَى أَبِي الْعَاصِزَوْجِهَا بِنِكَاحِهَا الْأَوَّلِ بَعْدَ سَنَتَيْنِ وَلَمْ يُحْدِثْ صَدَاقًا  

"The Prophet returned his daughter Zainab to Abul-As bin Ar-Rabi after six years in the first marriage without renewing the marriage." (Using translation from Tirmidhī 1143)   

«رَدَّ النَّبِيُّ ﷺ ابْنَتَهُ زَيْنَبَ عَلَى زَوْجِهَا أَبِي الْعَاصِ بْنِ الرَّبِيعِ بِالنِّكَاحِ الْأَوَّلِ وَلَمْ يُحْدِثْ شَيْئًا» صحيح  

"أَنَّ النَّبىَّ ﷺ رَدَّ ابْنَتَهُ زَيْنَبَ عَلَى أَبِى الْعَاصِ بَعْدَ سَنَتَيْن بِنِكَاحِهَا الأَوَلِ".  

"عَنِ ابْنِ عَبَّاسٍ قَالَ: رَدَّ رَسُولُ الله ﷺ ابْنَتَهُ زَيْنَبَ عَلَى زَوْجهَا أَبي الْعَاصِ بْن الرَّبيعِ بَعْدَ ست سنِينَ بِالنِّكَاح الأوَّلِ، لَمْ يُحْدِثْ شَيْئًا".