Your code work properly on english clients only, because i.e. GetZoneText gives the name of the zone in the wow client language
so a

"if zone == 'Shadowmoon Valley' or zone == 'Frostfore Ridge' or zone == 'Ashran'"

could never be true in another language. In german i.e. it called "Schattenmondtal". "Frostfeuergrad", "Ashran"

Same problem with the source variable (and others). You check only the english words.

This is a good point. I used IDs for actual mounts, but I need to work out how to get an ID for the zones.