If it's not stamped "ZC" on the block, it's not a real ZC. That's all there is to it. The SOHC ZC is basically the same as the USDM D16A6, and the DOHC ZC won't take a SOHC D16Z6 head very easily.
I've never actually SEEN a picture of a SOHC ZC VTEC engine... you're probably just thinking about a D16Z6 that someone's calling a SOHC ZC VTEC.
To get the 12:1 compression that you're talking about anyway, you'd have to run the DOHC ZC pistons in the D16Z6 block.