I've never heard of Zanzo but based on what appears to be TIG construction in conjunction with a straight fork and threadless headset, it is probably no older than mid-1990s. The downtube transitions from a vertical to horizontal oval, like Columbus max, but the rest rest of tubes appear to be normal. It could be a private label brand for a shop, but I'm not sure. The serial number may provide a clue to the origin. I'd also pull the fork to check for a manufacturer and date code, and check the bottom bracket thread standard and seat post size.