I for one think moving to such a big club would be bad for his career, and given his choice to remain at Zwolle in recent years, I think he certainly knows this too.
Of course it'd be great if hestepped up to a mid-table Spanish, German, Italian or maybe even Premiership team - but he is still young and has time to develop. He needs to do so incrementally and he especially needs to be playing week in, week out.
Look what happened to Marco at Stuttgard (yes he was injured a lot, but realistically, his chances of being a regular were pretty low from the start).
EDIT: Me can't spell