You only need one '=' character to check if something is equal

z.sh

@@ -38,7 +38,7 @@ _z() {
   # don't track excluded dirs
   local exclude
   for exclude in "${_Z_EXCLUDE_DIRS[@]}"; do
-   [ "$*" == "$exclude" ] && return
+   [ "$*" = "$exclude" ] && return
   done
 
   # maintain the file