after changing thermal zone in sketchup, the thermal zone list in OS still remains the same

edit

I'm not aware of a user script that does this but it would be pretty easy to add (see end of answer). However you can take a different approach to creation and assigning of zones.

1. Create zones that have multiple spaces and assign those spaces to the zone.
2. When all multi-space zones have been made and assign then run the Add New Thermal Zone For Spaces With No Thermal Zone user script to create and assigns zones for the remaining spaces.

With this approach there shouldn't be a need to delete any zones. If you want to write script to delete un-used zones would look something like this.

model.getThermalZones.each do |zone|
  if zone.spaces.size == 0 then zone.remove end
  # could add further check for non zero floor area and for more than 1 space surface
end