I have a reference manual "Light Gage Structural Steel Framing System Design Handbook" put out by the Light Gage Structural Institute that has all types of information on different shapes (Zees included)Don't know if they are even still around, the manual is copyrighted 1990. The address given is P.O. Box 9052 Dallas, Texas 75209. The Phone number shown is 214-520-2341 and the fax is 214-520-1979. At the time I bought it, the price was $5.00
The manual offers information on different shapes, design formulas, lap information, section properties,sample calculations, load tables etc. It might be outdated but the principles are still valid. You might try the number above or google the name.