How to add two separate GA accounts in one Drupal site
Go to /admin/config/system/googleanalytics > ADVANCED SETTINGS > CUSTOM JAVASCRIPT CODE > Code snippet (after)

ga('create', 'UA-XXXXXXXX-Y', 'auto', {'name': 'foo'});
ga(function(foo) {
  foo.send('pageview');
});
ga('create', 'UA-XXXXXXXX-Y', 'auto', {'name': 'bar'});
ga(function(bar) {
  bar.send('pageview');
});


This worked for me.