All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
There is no contradiction between these ahaadeeth; according to most scholars, the indication of the number in the ahaadeeth is not intended as a specific number. This means that a martyr may have more than 72 wives from al-hoor al-ʻiyn (women of Paradise); the hadeeth states this specific number because it is the least number given to the martyr, who shall be endowed with other great pleasures as well.
Al-Qaari wrote, "The number 72 in the hadeeth denotes that it is meant to indicate a specific and exact quantity, and not merely to signify abundance. It is interpreted to mean that the least number of wives the martyr shall have in Paradise from al-hoor al-ʻiyn is 72 and that Allaah may bless some with a greater number of wives as He wishes."
Some ahaadeeth indicated that the least number of wives that shall be given to the believer in Paradise is 72; others indicated a greater number, which amounts to 100 or more. There is no contradiction between these ahaadeeth; Allaah, The Exalted, bestows His grace upon whomever He wishes.
Al-Haafith Ibn Hajar wrote:
"As for the hadeeth which reads, 'Each shall have two wives (from the women of the worldly life),' (Imaam) Ahmad narrated a marfooʻ hadeeth (i.e. a hadeeth directly attributed to the Prophet ) with a different chain of narration on the authority of Abu Hurayrah in which the Prophet said, 'The one in the lowest rank among the people of Paradise will have 72 wives from among al-hoor al-ʻiyn, along with his wives from the worldly life...' Among the reporters of this hadeeth was Shahr ibn Hawshab, who was criticized by some scholars. Abu Yaʻla also cited the lengthy marfooʻ hadeeth about as-Soor (the trumpet into which the angel Israafeel  will blow on the Day of Judgment) with a different chain of narration on the authority of Abu Hurayrah as well stating that the man will have 72 wives from al-hoor al-ʻiyn created by Allaah and two wives from the children of Aadam (Adam) in Paradise. Abu Saʻeed reported that the Prophet said, 'The smallest reward for the people of Heaven is an abode where there are 80,000 servants and 72 wives...' [At-Tirmithi said: 'It is a ghareeb hadeeth']. Al-Miqdaam ibn Maʻdi Karib narrated that the Prophet said that the martyr shall receive six blessings in Paradise, one of which is that he shall have 72 wives from al-hoor al-ʻiyn. Moreover, Abu Umaamah narrated that the Prophet said: 'Everyone who shall enter Paradise will be given 72 wives from al-hoor al-ʻiyn and two from the women of the worldly life.' It was cited by Ibn Maajah and Ad-Daarimi with a very weak chain of narration.
The maximum number in this regard was cited by Abu Ash-Shaykh in Al-ʻAthamah and Al-Bayhaqi in Al-Baʻth on the authority of ʻAbdullaah ibn Abi Awfa attributed to the Prophet and it indicates that a resident of Paradise will have 500 wives from al-hoor al-ʻiyn or 4,000 virgins and 8,000 non-virgins, but the name of one of the reporters in its chain of narration is missing. Also, At-Tabraani reported on the authority of Ibn ʻAbbaas that a man from the dwellers of Paradise will reach 100 virgins in a single day." [Fat-h Al-Baari]
Allaah knows best.