Nasai

This hadith, if authentic, may have been stated before the command regarding the prescribed punishments (hudud) was revealed. Now, however, the enforcement of hudud is indispensable. In such a case, this person will certainly be stoned (rajm), whether the slave woman was consenting or the intercourse was forced upon her; however, in the case of coercion, the slave woman will be pardoned, and in the case of consent and willingness, she will receive fifty lashes. But if the wife has declared her slave woman lawful (halal) for her husband, then instead of stoning, the husband will be given lashes, as has been mentioned in previous ahadith.

Benefit:
The statements of the Companions (radi Allahu anhum) differ regarding adultery (zina) with a slave woman owned by one’s wife.
Imam Shawkani rahimahullah has given preference to the ruling of Hazrat Nu’man bin Bashir radi Allahu anhu, and the reason for this is that, due to the husband’s authority (tasarruf) over the property of his wife, there exists a certain doubt (shubha). Therefore, the punishment of stoning (rajm) should not be carried out.
And Allah knows best.
For details, see: (Awn al-Ma’bud Sharh Sunan Abi Dawud: 12/96, 99)

This hadith is somewhat different from the first hadith. According to the previous hadith, due to consent and willingness, the slave woman would become the wife of the man. And according to this hadith, she would remain a slave woman. However, since this hadith is no longer applicable and is abrogated, any difference between them has no effect. In any case, according to many researchers, both of these narrations are weak.