@leo,

You can overlay the zoom-back button on top of reset button to perform zoom-out step-by-step on clicking reset button. Please find the code snippet below.

function back(){
  var viewportMinStack = chart.options.viewportMinStack;
  var viewportMaxStack = chart.options.viewportMaxStack;
  //if(!chart.axisX){
  //		chart.axisX = {};
  //	}
  if(viewportMinStack.length>1){
    viewportMinStack.pop();
    viewportMaxStack.pop();
    axisX.viewportMinimum = viewportMinStack[viewportMinStack.length-1];
    axisX.viewportMaximum = viewportMaxStack[viewportMaxStack.length-1];
  }
  else{
    axisX.viewportMinimum = null;
    axisX.viewportMaximum = null;
    document.getElementById("button").style.visibility = "hidden";
  }
  chart.render();
}
var button = document.getElementById( "button" );
button.addEventListener("click", back);
document.getElementsByClassName("canvasjs-chart-toolbar")[0].lastChild.style.visibility = 'hidden';

Please take a look at this updated JSFiddle for complete code.

—
Vishwas R
Team CanvasJS