I think that Zach's bizarre infatuation with shoes and socks is another expression of his main goal in life: to make it to adulthood by age three. He will do anything and everything that makes him feel like he is a grown-up, without regard for the generally accepted norms of behavior (for example, not using sweaty socks as gloves!). As a father, this is rather wonderful as it provides years worth of material to hold over his head when he actually begins to approach adulthood! Behold the latest examples of the shoes and socks fascination:
