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.