code: public DateTimeFormatterBuilder appendZoneText(TextStyle textStyle,
                                                     Set<ZoneId> preferredZones) {
          // TODO: preferred zones currently ignored
          Jdk8Methods.requireNonNull(preferredZones, "preferredZones");
          appendInternal(new ZoneTextPrinterParser(textStyle));
          return this;
      }
docs: Appends the time-zone name, such as 'British Summer Time', to the formatter.
  <p>
  This appends an instruction to format/parse the textual name of the zone to
  the builder.
  <p>
  During formatting, the zone is obtained using a mechanism equivalent
  to querying the temporal with {@link TemporalQueries#zoneId()}.
  If the zone is a {@code ZoneOffset} it will be printed using the
  result of {@link ZoneOffset#getId()}.
  If the zone is not an offset, the textual name will be looked up
  for the locale set in the {@link DateTimeFormatter}.
  If the temporal object being printed represents an instant, then the text
  will be the summer or winter time text as appropriate.
  If the lookup for text does not find any suitable result, then the
  {@link ZoneId#getId() ID} will be printed instead.
  If the zone cannot be obtained then an exception is thrown unless the
  section of the formatter is optional.
  <p>
  During parsing, either the textual zone name, the zone ID or the offset
  is accepted. Many textual zone names are not unique, such as CST can be
  for both "Central Standard Time" and "China Standard Time". In this
  situation, the zone id will be determined by the region information from
  formatter's  {@link DateTimeFormatter#getLocale() locale} and the standard
  zone id for that area, for example, America/New_York for the America Eastern
  zone. This method also allows a set of preferred {@link ZoneId} to be
  specified for parsing. The matched preferred zone id will be used if the
  textual zone name being parsed is not unique.
  <p>
  If the zone cannot be parsed then an exception is thrown unless the
  section of the formatter is optional.
  
  @param textStyle  the text style to use, not null
  @param preferredZones  the set of preferred zone ids, not null
  @return this, for chaining, not null