Two new ZnII–LnIII heterometallic complexes derived from the amine-phenol ligand, namely [Zn2Ln(L)2(H2O)2](ClO4)3·3.5H2O (Ln = Dy (1) and Tb (2), H2L = 1,2-bis(3-methoxysalicylideneethylaminooxy)ethane), have been synthesized and structurally characterized. Complexes 1 and 2 are isomorphic trinuclear clusters and crystallize in the triclinic P space group. Magnetic measurements indicate that complex 1 exhibits field-induced slow magnetic relaxation with energy barrier of 27.91 K. Both display strong fluorescence emissions, which are typical narrow emission bands of lanthanide ions. Moreover, complex 2 shows a proton conductivity of 6.43 × 10−5 S cm−1 at 60 °C and 98% relative humidity. Complexes 1 and 2 as multifunctional materials may offer a potential application in magnetic, luminescent, and electrical devices.