code: public static TimeZone toTimeZone(ZoneId zoneId) {
          String tzid = zoneId.getId();
          if (tzid.startsWith("+") || tzid.startsWith("-")) {
              tzid = "GMT" + tzid;
          } else if (tzid.equals("Z")) {
              tzid = "UTC";
          }
          return TimeZone.getTimeZone(tzid);
      }
docs: Converts a {@code ZoneId} to a {@code TimeZone}.
  
  @param zoneId  the zone, not null
  @return the time-zone, not null