In my case exact error was below
':android:transformClassesWithJarMergingForDebug'.
com.android.build.api.transform.TransformException: java.util.zip.ZipException: duplicate entry: com/google/android/gms/internal/zzqx.class
I was using another version of google apis i.e. in one modules gradle file
if (!project.hasProperty('gms_library_version')) {
ext.gms_library_version = '8.6.0'
}
however in other modules version 11.6.0 as below
compile "com.google.android.gms:play-services-ads:11.6.0"
compile "com.google.android.gms:play-services-games:11.6.0"
compile "com.google.android.gms:play-services-auth:11.6.0"
However to find this i did a ctrl + n in android studio and entered class name zzqx.class and then it displayed 2 jar files being pulled for this class and then i understood that somewhere i am using version 8.6.0 . On changing 8.6.0 to 11.6.0 and rebuilding the project the issue was fixed .
Hope this helps .
More on this here https://www.versionpb.com/tutorials/step-step-tutorials-libgdx-basic-setup-libgdx/implementing-google-play-services-leaderboards-in-libgdx/