Write the net ionic equations for the reaction of Na2S(aq) with Pb2+(aq) and Zn2+(aq)?

Net ionic equation for the reaction of Na₂S(aq) with Pb²⁺(aq) :
Pb²⁺(aq) + S²⁻(aq) → PbS(s)

Net ionic equation for the reaction of Na₂S(aq) with Zn²⁺(aq) :
Zn²⁺(aq) + S²⁻(aq) → ZnS(s)

Double replacement....

Someone might be tempted to write something like this:
Pb2+ + S^2- --> PbS(s)
... but that isn't the case.

Sodium sulfide dissolves in water to make Na+ ions and HS^- ions along with OH- ions. Sulfide ion (S^2-) is too basic to exist in water. Instead, it reacts with water, making HS^- and OH-. HS- ion will react with other metal ions. Metal sulfides are extremely insoluble, so insoluble PbS and ZnS will prevail instead of the hydroxides.

HS^- + OH- + Pb2+ --> PbS(s) + HOH(l)
HS^- + OH- + Zn2+ --> ZnS(s) + HOH(l)

But you'd better work fairly fast since a solution of sodium sulfide will produce hydrogen sulfide gas which is liberated to the atmosphere and makes the room smell really bad. Therefore, it should be handled in a hood.

Na2S(s) + HOH <==> 2Na+ + HS^- + OH-
HS^- + HOH <==> H2S(g) + OH-