A documentation bug has been reported and we’re told it is fixed and so will appear soon, one hopes, in the web-available version of the docs. Time.zone() does not return a value, so there is nothing to be printed. Here is the example from the current docs.
// Set time zone to Eastern USA daylight saving time
Serial.print(Time.zone(-5));
There is another documentation bug, or an undocumented feature. Does Time.zone() return the time offset from GMT, or does it return the legal time for the timezone at that offset? Is the comment in the doc correct? Is daylight savings time returned or not. It ought not to return DST because many offsets from GMT have varying DST rules. E.g. I know +2 has some countries which have DST and some which don’t.