Catalyzes the reductive cleavage of azo bond in aromatic azo compounds to the corresponding amines. Requires NADPH, but not NADH, as an electron donor for its activity. Homotetramer. Part of the yhcYZ-yhdA operon that is induced by the two-component regulatory system LiaS/LiaR in response to cell envelope stress. Belongs to the azoreductase type 2 family.