Which version of ZA suite do you have ?
You can download a manual
here which will tell you how to configure ZA.
A quick look at the manual, gives you this information, on page 70 (using the 6.5 version) you will need to know which ports mIRC uses, to allow it access. Although, from your post, it looks like port 6667. Do a google, or look in mIRC's help file, for help in selecting the correct ports.