There are new country codes RS for Serbia and ME for Montenegro.

http://www.iso.org/iso/en/prods-services/iso3166ma/03updates-on-iso-3166/nlv12-div.htm

I would suggest the following changes:

In zone.tab

Change the line:

CS    +4450+02030    Europe/Belgrade

to:

RS   +4450+02030    Europe/Belgrade

Add:

ME +4247+01928 Europe/Podgorica


In europe

Add:

Link    Europe/Belgrade    Europe/Podgorica


Mark