It's building for Android with crosswalk runtime. For crosswalk the it builds for arm and x86 architectures, so you get 2 APKs. To build for Android only uncheck the checkbox "Optimize with Crosswalk" at the top of the build settings.
What you got earlier was a crosswalk build. When you have "optimize for corsswalk" checked and you build for Android, you get the Android with crosswalk build. For crosswalk you get a zip file which contains two APKs, one for Arm architecture and one for x86 architecture.
If you download the crosswalk build via the UI (in v3088), you should get a zip file. Alternately, you can download the build via email where you will get the following options:
The Cordova Android build for xxx was successful.
You can download your application Zip file with this secure link.
You can download your application ARM file with this secure link.
You can download your application x86 file with this secure link.
You can download your application Log file with this secure link.
The arm and x86 builds will download an apk file.
It sounds strange that you are getting zip through email but not through the build interface. Can you please check if your download is complete. Sometimes the file is given temporary name till the download finishes.