index.js

window.onwheel = function (e) {
  e.preventDefault();

  if (e.ctrlKey) {
    // Your zoom/scale factor
    scale -= e.deltaY * 0.01;
  } else {
    // Your trackpad X and Y positions
    posX -= e.deltaX * 2;
    posY -= e.deltaY * 2;
  }

  render();
};

Nice, thanks!