The departure of Zin to me indicates two scenarios, one less likely than the other.
The first is that despite denials everything has already been done very, very discreetly, between Bloom and Txixi, Potter and Pep (indirectly), and that a deal is in place behind the scenes, with an agreed fee, the exact nature of which neither set of supporters will most likely ever know. There'll be figures bandied around in the media to make both sets of supporters feel good, doubtless. Only thing being waited for: for them to get a decent full back.
Second scenario is that there is no deal whatsoever in place or even progressing for Cucu, but that Aké's remaining with us was dependent on — or at least shored up by — assurances of more game time, if not at centre half, then at left back. He is well capable of occupying this position, and has proven it. He has weaknesses where Zin had strengths, but he also has strengths where Zin had weaknesses. I agree that this is the less plausible of the two.
Worst case scenario: there is also Cancelo. Not because he's no good on the left, far from it, but because if Walker gets injured again we are in the shit.
If neither scenario can be envisaged, and if no-one else is being seriously looked at, then I have to say that I'm completely nonplussed by Zin's departure.