Which metal, al or ni, could reduce zn2+ to zn(s) if placed in a zn2+(aq) solution?

If placed in a Zn²⁺ solution for the oxidation number of Zn to reduce from +2 to 0, a displacement reaction should happen.
displacement reaction is when one species can displace another species from its compound and take the place of the species in the compound. For one metal to displace another metal from its compound, the metal displacing should be more reactive than the metal being displaced. 
In this case Al is above Zn in the reactivity series and Ni is below Zn in the reactivity series, This means that Al is more reactive than Zn and Zn is more reactive than Ni.
Therefore Al can displace Zn in its Zn²⁺ form and displace it to its Zn solid form.
Al can reduce Zn²⁺ to Zn