Yeah seeing as though its a modified zed you won't go upsetting any loyalists by shaving the door locks and electrifying it.
Keyless entry is really the only way to go, it doesnt stop it, but it certainly acts as a deterant...
Sorry to hear about the door though, its a real ball breaker when they do enough damage to piss you off, but not enough to make the increased premiums caused by an insurance claim worthwhile..
Plan B, would be to insure your car for so much that you can beg people on the street to steal it.
Either way I think this may not be such a bad thing in the long run as it will probably urge you to make your car more secure, and it didnt take them stealing it to show you..