If I update the Time Zone Database using ziupdater.jar with a new tzdata.tar.gz from the IANA, do I need to restart the JVMs to see the new data?
Almost certainly. Any application which uses a java.time.ZoneId to get the java.time.zone.ZoneRules for a location will have initialized the rules using a java.time.zone.ZoneRulesProvider. The Javadoc for the ZoneRulesProvider makes this observation:
Many systems would like to update time-zone rules dynamically without stopping the JVM. When examined in detail, this is a complex problem. Providers may choose to handle dynamic updates, however the default provider does not.