Zeus was some cool stuff and some people are really into it. As you noticed, Spanish made, a competitor to Campagnolo at a lower price. Ron Kitching imported it into England and made it popular. The 2001 parts were supposed to be pretty nice, lower end parts were labeled Alfa. There are Zeus catalogs on the web, you may be able to identify the frame. Reynolds was used, but also some lesser tubing I believe.

My advice would be to restore it, decals turn up frequently on ebay, and you'll have a wonderfully cool piece!

My Zeus on Classic Rendezvous:

http://www.classicrendezvous.com/Spa..._bike_side.htm