Could Zuckerberg be jailed as a result of this hearing? For instance, in case of him being previously aware of Europeans data leakage or deliberately lying about it?
While the EU parliament doesn't jail people, there are lots of countries that do.
If he admits to breaking the law during the meeting any one of the EU countries could issue an EU arrest warrant for him. Then he would be held within that country to be extradited.
If I was in charge of the British Parliament committee that wants to question him, I would issue an EU arrest warrant for one of the many crimes that are being levelled at Cambridge Analytic with him being part of it. Then question him about it. But I am petty and would want to show that just because he's American he isn't always out of reach.
The entire assumption is Facebook isn't breaking any criminal laws and Mark Zuckerberg isn't directly linked to those laws.
Chances of going to jail, slim. But it is still in the world of possibilities.
I'm not saying that, you're saying it and it's not going to happen any more than him stabbing someone or all of Belgium getting eaten by bears.