The correct name is ZuCable, rather than ZCable. I tried contacting them as a dealer inquiry, but didn't hear back.
I am sceptical about their all copper spades (no plating). What I've heard they believe, and it's pretty much true, is that where the copper is tightly sealed against the binding post and nut, it's air-tight and won't oxidize. Sound still has to travel over though the spade to get to the binding post though, and the higher frequencies will travel along their surface. Since oxidation can occur in the open area where it is not air-tight, it seems vulnerable to oxidation, which will hinder the sound. It would be interesting to hear what they have to say in this regards.