Aristotle on unity in <scp> <i>Metaphysics</i> </scp> Z.12 and H.6

Aristotle's inquiry into the definitional question “what is substance?” in central books of Metaphysics constrained by unity requirement. Roughly, a particular hylomorphic compound substance, such as this human, ought to be unified whole and not just heap material parts form. A similar claim applies substance-kind, which ΖΗΘ characterises taken universally. I raise following about picture unity: Is compound's basic or it derived from form's unity? Reading closely Z.12 H.6, argue that form explanatorily for unity.