My path is cd ~/.buildozer/android/platform/android-sdk-21/build-tools/19.1.0/
the name of my apk is   MyApplication-0.1-release-unsigned.apk 
the path of apk is   /home/kivy/Desktop/provaAPP/bin
Something like ~/.buildozer/android/platform/android-sdk-21/build-tools/19.1.0/zipalign -v 4 /home/kivy/Desktop/provaAPP/bin/yourapkname.apk youroutputapkname.apk, I think.
How to zipalign a Apk with kivy buildozer?