Rule1 = {z -> Interpolation[Table[{i, i^2 + i}, {i, 0, 2, 0.1}]]};

Rule2 = {x -> Interpolation[Table[{i, Sin[i] + i}, {i, 0, 2, 0.1}]]};

func = Sin[x z]/(x + z)^2 /. Flatten[{Rule1, Rule2}]

Rule1z = Interpolation[Table[{i, i^2 + i}, {i, 0, 2, 0.1}]];
Rule2x = Interpolation[Table[{i, Sin[i] + i}, {i, 0, 2, 0.1}]];
fun[i_] = Sin[Rule2x[i] Rule1z[i]]/(Rule2x[i] + Rule1z[i])^2;
fun[1.2]

(* -0.0267361 *)

Rule1 = {z -> Interpolation[Table[{i, i^2 + i}, {i, 0, 2, 0.1}]]};
Rule2 = {x -> Interpolation[Table[{i, Sin[i] + i}, {i, 0, 2, 0.1}]]};
RuleAz = z /. Rule1;
RuleBx = x /. Rule2;
fun2[i_] = Sin[RuleBx[i] RuleAz[i]]/(RuleBx[i] + RuleAz[i])^2;
fun2[1.2]

(* -0.0267361 *)

fun3[i_] = Sin[x[i] z[i]]/(x[i] + z[i])^2 /. Flatten[{Rule1, Rule2}];
fun3[1.2]

(* -0.0267361 *)