All I can say is the password protected zip either, isn't protected, or yahoo mail couldn't scan it, so it might be using just the fact that there is an .exe file inside the zip and jumping on that.
The submission to VT should eventually get to avast as those AVs that don't detect it should have a sample sent by VT. Not ideal so it is best to try and send the sample directly, though I don't know how you would get round the problem. You could try renaming the sample to AntvrsInstall-exe.old and use a different zip archive (7zip, etc.) to password protect it.