I'm not sure what I'm missing - some user error. According to the TC documentation I should be able to have my Assemblies.zip artifact from one build used as a Build Dependency in anothe build, and using the Assemblies.zip!** notation it should unpack the .zip contents at the build configuration root. For some reason it seems to be leaving the artifact all zipped up and my build fails to access the dlls inside. Here's a screen shot of my Dependency and the "Check artifact dependencies" output which seems to indicate the archive remaining zipped rather than unpacked.
I appreciate any help you can provide.