well, if you right click on the zip file (explorer) and choose > scan, AVAST should warn you.
If you only opened the zip file, and didn't excecute Eicar file,, than AVAST resident provider will not detect it.
If you launch the Eicar file, AVAST will warn you.
The resident protection only works on executed (running)programs, this means it uses no memory scan.
I hope this is a answer to your question.
Waldo