Extending ZeptoScroll (https://github.com/suprMax/ZeptoScroll) to support horizontal and vertical scrolling.

zepto.scrollBoth.js

;(function($) {
  var interpolate = function (source, target, shift) { 
    return (source + (target - source) * shift); 
  };

  var easing = function (position) { 
    return (-Math.cos(position * Math.PI) / 2) + .5; 
  };

  $.scrollBoth = function(XY, duration, easingF) {
    var endX = XY[0], endY = XY[1];
    duration = duration || 200;
    (typeof easingF === 'function') && (easing = easingF);

    var startY = window.pageYOffset, startX = window.pageXOffset,
      startT  = Date.now(), finishT = startT + duration;

    var animate = function() {
      var now = +(new Date()), shift = (now > finishT) ? 1 : (now - startT) / duration;
      window.scrollTo(interpolate(startX, endX, easing(shift)), interpolate(startY, endY, easing(shift)));
      (now > finishT) || setTimeout(animate, 15);
    };

    animate();
  };
}(Zepto));