The ZDA is a Zastava pistol which are now imported by EAA and called the EZ series. They were called the CZ99, CZ999 Scorpion and a few other things. They are very good guns although EAA's customer service leaves lots to be desired.
The design is a cross between a Sig 226 and a Walther P-88, and has worked very well. Check out this website for more information on these and other Zastava pistols. www.CZ999.org. I have a South African version (built under licence by Tressitu) called a TZ99, It is by far the best shooting pistol I have!