Complex sentence: In January 2016, Holland became Assistant Manager to Guus Hiddink for the remainder of the 2015--2016 season and in July 2016 Holland became Assistant to Antonio Conte.
Split into simpler sentences: In January 2016 Holland became Assistant Manager to Guus Hiddink for the remainder of the 2015--2016 season. In July 2016 Holland became Assistant to Antonio Conte.