You won't find it on the web. Zenithink is not at large as Apple which can cover whole production stages from designing, prototyping, manufacturing to wholesales. Actually they're actively seeking OEM partnership with larger brand for one of their VLSI ZT-180a since 2009 (yes, prior to official iPad announcement). What you've seen is not a prototype but a finished product after they've secured the fundings. You can considered this one is a manufacturing by-product of other OEM products which outsiders have no knowledge with.

In fact, it's pretty late if they're still talking about prototypes now, because according to manufacturers' news in China big brand like Huawei (attached) and ACorp are already manufacturing iPad clones.