Michael, G7VJR, the Club Log guru tweeted on 2018, Jan. 23:
"Provisional arrangements: Z6 maps to REPUBLIC OF KOSOVO, using country code 522, with a start date of 2018-01-21 00:00:00. This is subject to change when ARRL release the technical data but is based on all the info I have today."
CQRlog is sure among the very first loggers resolving Z6 properly and, in accordance with ClubLog/G7VJR introduces Rep. of Kosovo as a regular DXCC Country since 2018-01-21 00:00:00 (subject to change when ARRL release the technical data).
73, Martin, OK1RR