I get what you mean, you have a point, but Zinch was a bit part player last season before February. Cancelo was one of the first names on the team sheet. If we sign a new LB, Zinch minutes will be reduced.
However, if we are not able to sign that new LB for an acceptable fee, why not keep Zinch? He can play in midfield if push comes to shove.
The good news is that we'll know over the next 7-10 days whether we'll buy Cucu or keep Zinch. Arsenal are waiting and City/Zinch have to decide over the next few days.