EDIT: I got it working!
I had 2.0-test4 compiling successfully before using the original post's compile instructions (plus obviously the changes made to src.pro since then), but I see on 6/24/2012 there was a change from luazip to quazip made by chris. The src.pro from that point actually points to:
To get it to compile, I had to do three things:
1) modify the src.pro by adding -lquazip \ to the win32:LIBS:
2) downloading the quazip--0.4.4 source from quazip.sourceforrge.net, and unzipping the quazip-0.4.4 folder so that it matches the src.pro location (C:\mudlet_packages\includes\quazip-0.4.4\quazip).
3) Copy the already-compiled quazip.dll file from the current mudlet 2.1 windows EXE release (easiest way to grab this is to install mudlet 2.1 on your system) into the C:\mudlet_packages\mudlet_libs folder.