Plant hardiness and heat tolerance span a range of zones and are thus specified with a description like "Zones 06a-09b" or "AHS 06-09".  The drop-down combo-boxes used to specify and display climate zones allow you to enter descriptions just like this.

Because the drop-down list only shows the individual zones, you'll have to specify zonal ranges by typing the codes in the text-entry portion of the combo-box.  The color-patches are automatically assigned when you press the <TAB> key and go to the next field. ................................

Here's what the results will look like:

The Sunset climate zones that an individual species is adapted to are frequently discontinuous ranges.  For example, the coldest climate zones would include zones 01-02, zone 15, and zones 44-45.  Here's how multiple zonal ranges will look:

There are six climate fields that allow multiple codes: