Crouch cancel. Do anything you can do to screw with his spacing. You have to remember Zhu plays a mean Falco too, so he knows the set-ups, and knows where the weak points are, so you have to be extra careful. I don't try to go for big combos on characters like Marth and Peach, because if you screw up at any point, you might as well kiss your stock good bye. Laser a little more, work in some up-tilts, back air really shines here, and if you are charging his shield with an aerial, DO NOT FAST FALL. I know it will mess with your l-cancels for a while, but what's better: Getting Shield grabbed, or not getting shield grabbed? All in all, just play smart and careful, and try and trick him into missed f-smashes. Treat every stock like your last.