2hours resume for newbies (like me) :
If you type this command :
zipalign -v 4 platforms/android/app/build/outputs/apk/release/app-release-unsigned.apk app-release.apk
Witch gives you :
command not found: zipalign
It's maybe that the path is somewhere wrong.
If you have this :
Unable to locate an executable at "/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/bin/apt" (-1)
It confirms that its not really as it should be. So, to execute zipalign and finally publish your app, you have to go in the correct repository and execute commande.
1. Go to the correct repo to execute command :
The path is cd /Users/xxxyour_user_namexxx/Library/Android/sdk/build-tools/xxxxx/
cd /Users/greg/Library/Android/sdk/build-tools/28.0.3
2. Execute your zipalign command, don't forget to precise the path of apk file :
Obviously, chance "greg" and "myapp" with your user name & app name.
./zipalign -v 4 /Users/greg/Desktop/AppLocal/myapp/platforms/android/app/build/outputs/apk/release/app-release-unsigned.apk /Users/greg/Desktop/AppLocal/myapp/platforms/android/app/build/outputs/apk/release/app-release.apk
Hope it helps.