Sunday s strike was Haller s sixth goal in 10 league appearances since leaving West Ham for Ajax in a club-record transfer deal in January.
After Dusan Tadic set up Ryan Gravenberch for The Lancers opening goal in just the fifth minute, Haller, who also has five league assists to his name so far, finished off a 54th-minute effort to make it 2-0 after being set up by David Neres.
Tadic then registered a goal of his own and his club s third goal in the 77th minute before Ahmed El Messaoudi pulled a goal back for Groningen six minutes to full-time.
While Haller lasted for the entire duration of the games, Ghana sensation Kudus, who picked up a 48th-minute yellow card, was substituted by Jurgen Ekkelenkamp in the 63rd minute.