Lechwes and Kobs are in the same genus, they are in the genus Kobus, but like Zebraduiker said, that is for sure a Nile lechwe (Kobus megaceros) and not a White eared kob (Kobus kob leucotis), no european zoo ever had White eared kob, but 2 american zoos did
I know them as Mr Grays Waterbuck and remember small groups at Zoo Wassenaar ( now closed ) and Zoo Hannover but this is many years ago.
Beautifull photo by the way Zebraduiker !