docs: public static int validateZone(CharSequence zone) {
  		for(int i = 0; i < zone.length(); i++) {
  			char c = zone.charAt(i);
  			if (c == IPAddress.PREFIX_LEN_SEPARATOR) {
  				return i;
  			}
  			if (c == IPv6Address.SEGMENT_SEPARATOR) {
  				return i;
  			}
  		}
  		return -1;
  	}