When you call a method, you pass it a value that it receives in the variable it declares in it's method header:
private void GetZoneTag(string ZoneArea)
Inside the method, the value is called "ZoneArea" but that variable does not exist outside the method itself. To call it, you pass it an actual value:
GetZoneTag("Hello world");
Or
string zoneName = "Hello World";
...
GetZOneTag(zoneName);
Whee you get the value from, I don;t know - I have no access to the rest of your code!