googlemaps-scroll-trackpad-issue-zoom.js

// Just set the pointer-events: none CSS to the <iframe> to disable mouse scroll.

/*
<div id="gmap-holder">
    <iframe width="100%" height="400" frameborder="0" style="border:0; pointer-events:none"
            src="https://www.google.com/maps/embed/v1/place?q=XXX&key=YYY"></iframe>
</div>

If you want the mouse scroll to be activated when the user clicks into the map, then use the following JS code. 
It will also disable the mouse scroll again, when the mouse moves out of the map.

*/
  $('#gmap-holder').click(function(e) {
    $(this).find('iframe').css('pointer-events', 'all');
  }).mouseleave(function(e) {
    $(this).find('iframe').css('pointer-events', 'none');
  });