Why only As⁺³ gets precipitated as As₂S₃ and not Zn⁺² as ZnS when H₂S is passed through an acidic solution containing As⁺³ and Zn⁺²?

(1) Solubility product of As₂S₃ is less than that of ZnS
(2) Enough As⁺³ are present in acidic medium
(3) Zinc salt does not ionise in acidic medium
(4) Solubility product changes in presence of an