SELECT COUNT (DISTINCT ZUSER) in core data

I'm new in core data I'm converting my sql query to fetch the coredata results but not able to convert this query.

SELECT COUNT (DISTINCT ZUSER) AS Users,ZHOUR ,SUM ( ZLIKE) As Likes FROM ZUSERLIKE where ZDAY=28 AND ZMONTH=2 AND ZYEAR=2015 GROUP BY ZHOUR

Any expert can help me out the problem I'm facing at COUNT (DISTINCT ZUSER) this point.