It crashes, there are a few changes required in zr_nade_RestrictCanUse:
PHP Code:
// If the player is a zombie
if (ZR_IsClientZombie(client)){
return Plugin_Continue; // you need to return an action, not return nothing.
}
PHP Code:
new Action:result;
Call_Finish(result); // get the result from ZR's function and return it.
return result;
I've also removed the hook/unhook functions in zr_nade_RestrictCanUse. One of those caused the crashes - and they aren't really needed.
Once I got it running, it spawned a grenade, but doesn't seem to actually unhook ZR's hook. Weapons are still blocked for zombies. I added a few print statements to see if your plugins hook worked. It did and returned Plugin_Continue (allow pickup) as expected. But ZR's hook was also called (after your plugin), which blocked pickup.
The SDKUnhook function doesn't tell if it actually unhooked something. This would be nice to know. A debug build of SDK Hooks should print this to the console though.