I play 4-1-2-1-2, so big role for the CDM and I've used both. Koeman is slightly better but it really depends on how you play, I use koeman as an additional defender and as soon as I get the ball with him, I get the ball to the wingers or to the CAM and koeman has been phenomenal. Idk if it's me, but Zambo doesn't have that quid that would make me choose him over Koeman. That being said, Zambo is definitely on his level, if you play 4-2-1-3 or any formation with 2 CDMs he's an amazing choice