I think even if they're mostly interacting in a professional context, that doesn't preclude them drinking together (see also Shen Wei and the chancellor(?)), but if they do, they probably mostly talk work, politics and current events. I can imagine ZXC casually asking, "So, how's my son doing? Is he causing you any trouble?" kind of questions, without it going remarked upon. That wouldn't necessarily imply an estranged relationship -- just that he wants ZYL's direct boss's POV. You know?