I’d cut its arms off entirely to begin with rather than tie them up.
As for the skateboard:
1.) How would it move on anything other than pavement, ex: grass.
2.) How would it stay upright on the skateboard?
3.) How to limit the directional control of the zombie? Skateboard could still drift to the left or right, if not outright turning around.
I just came up with a potential solution though: Remote control.
Super glue some earbuds into its ears, and duct tape an MP3 player to its back, with a radio controlled switch wired into each earbud cable. Then just steer it left and right by varying which ear is getting sound with a remote control or a laptop or something. All you would have to do is slap a vest with dynamite or remote C-4 on it, release it, and guide it to the target.
You could do the same thing only with a camera or something duct taped to its head instead, and boom, instant meat-probe for exploring cities from safety.