How to draw polygon on google map in iOS, postcode wise in iOS

I am working on a map display where I have a zip list and I want to highlight an area of ​​each zip in the map. I am using google map. I have a list of zip codes. I really need the boundary coordinates of each zip.

the actual requirements are shown in the figure.

CLGeocoder *geoCoder = [[CLGeocoder alloc] init];
[geoCoder geocodeAddressString:@"94111" completionHandler:^(NSArray *placemarks, NSError *error) {

    GMSMutablePath *rect = [GMSMutablePath path];

    for (CLPlacemark* aPlacemark in placemarks)
    {
        // Process the placemark.
        CLLocation *location = aPlacemark.location;

        CLLocationCoordinate2D coordinate = location.coordinate;

        NSLog(@"Latitude %f", coordinate.latitude);

        NSLog(@"Longitude %f", coordinate.longitude);

        [rect addCoordinate:CLLocationCoordinate2DMake(coordinate.latitude, coordinate.longitude)];
    }

    // Create the polygon, and assign it to the map.
    GMSPolygon *polygon = [GMSPolygon polygonWithPath:rect];
    polygon.fillColor = [UIColor colorWithRed:0.25 green:0 blue:0 alpha:0.75];
    polygon.strokeColor = [UIColor blackColor];
    polygon.strokeWidth = 2;
    polygon.map = self.mapVew;


}];