Slave women owned by multiple people and paternal certainty

https://sunnah.com/abudawud:2270 In the above hadith a woman was owned by multiple people and had a child whose parentage was questionable. Would this not be considered Zina for multiple owners to cohabit with a slave girl since it would cause paternal uncertainty? Or was this not zina since the prophet only laughed at the situation? please provide proofs thanks.