global.js

jQuery(function($){
  
  	// Prevent Google Maps from hijacking scroll
	var onMapMouseleaveHandler = function (event) {
		var that = $(this);
		that.on('click', onMapClickHandler);
		that.off('mouseleave', onMapMouseleaveHandler);
		that.find('iframe').css("pointer-events", "none");
	}

	var onMapClickHandler = function (event) {
		var that = $(this);
		// Disable the click handler until the user leaves the map area
		that.off('click', onMapClickHandler);
		// Enable scrolling zoom
		that.find('iframe').css("pointer-events", "auto");
		// Handle the mouse leave event
		that.on('mouseleave', onMapMouseleaveHandler);
	}

	// Enable map zooming with mouse scroll when the user clicks the map
	$('.responsive-map').on('click', onMapClickHandler);

});

style.css

/* Map
--------------------------------------------- */

.responsive-map {
	position: relative;
	width: 100%;
	height: 0;
	padding-bottom: 75%; /* 450/600 */
}

.responsive-map iframe {
	position: absolute;
	pointer-events: none;
	top: 0;
	left: 0;
	width: 100% !important;
	height: 100% !important;
}