One idea I experimented with for this was to use airport codes. Airports are the approximate correct frequency (the kinds of political entities that might make decisions about timezones usually have an airport), quite recognisable to people familiar with the relevant area and have an established short code and canonical list.

There are disadvantages too of course, one of which is overlap between airport codes and currently existing timezone codes. This led me to discover a couple of airports that have the same code as their timezone.