how to zoom in on a complex svg structure

Question

Scaling in svg is done with viewBox, which combines both scaling and offset. There is a nice article How to Scale SVG.
From the following article:

If you think of the document as a canvas, the view box is part of the
canvas you want the viewer to see.

It’s like a screen of your cell phone in the camera app which shows part of the scene which is observed with specified scale and offsets.

enter image description here

Nice sample which demonstrates what is viewBox can be found here.

A little math and I implemented zoom in/zoom out with mousewheel. In addition added panning with mousemove and display scale value. An example which demonstrates how viewBox can be used:

const svgImage = document.getElementById("svgImage");
const svgContainer = document.getElementById("svgContainer");

var viewBox = {x:0,y:0,w:svgImage.clientWidth,h:svgImage.clientHeight};
svgImage.setAttribute('viewBox', `${viewBox.x} ${viewBox.y} ${viewBox.w} ${viewBox.h}`);
const svgSize = {w:svgImage.clientWidth,h:svgImage.clientHeight};
var isPanning = false;
var startPoint = {x:0,y:0};
var endPoint = {x:0,y:0};;
var scale = 1;

svgContainer.onmousewheel = function(e) {
   e.preventDefault();
   var w = viewBox.w;
   var h = viewBox.h;
   var mx = e.offsetX;//mouse x  
   var my = e.offsetY;    
   var dw = w*Math.sign(e.deltaY)*0.05;
   var dh = h*Math.sign(e.deltaY)*0.05;
   var dx = dw*mx/svgSize.w;
   var dy = dh*my/svgSize.h;
   viewBox = {x:viewBox.x+dx,y:viewBox.y+dy,w:viewBox.w-dw,h:viewBox.h-dh};
   scale = svgSize.w/viewBox.w;
   zoomValue.innerText = `${Math.round(scale*100)/100}`;
   svgImage.setAttribute('viewBox', `${viewBox.x} ${viewBox.y} ${viewBox.w} ${viewBox.h}`);
}


svgContainer.onmousedown = function(e){
   isPanning = true;
   startPoint = {x:e.x,y:e.y};   
}

svgContainer.onmousemove = function(e){
   if (isPanning){
  endPoint = {x:e.x,y:e.y};
  var dx = (startPoint.x - endPoint.x)/scale;
  var dy = (startPoint.y - endPoint.y)/scale;
  var movedViewBox = {x:viewBox.x+dx,y:viewBox.y+dy,w:viewBox.w,h:viewBox.h};
  svgImage.setAttribute('viewBox', `${movedViewBox.x} ${movedViewBox.y} ${movedViewBox.w} ${movedViewBox.h}`);
   }
}

svgContainer.onmouseup = function(e){
   if (isPanning){ 
  endPoint = {x:e.x,y:e.y};
  var dx = (startPoint.x - endPoint.x)/scale;
  var dy = (startPoint.y - endPoint.y)/scale;
  viewBox = {x:viewBox.x+dx,y:viewBox.y+dy,w:viewBox.w,h:viewBox.h};
  svgImage.setAttribute('viewBox', `${viewBox.x} ${viewBox.y} ${viewBox.w} ${viewBox.h}`);
  isPanning = false;
   }
}

svgContainer.onmouseleave = function(e){
 isPanning = false;
}

<span id="zoomValue">1</span>
<div id="svgContainer">
<svg id="svgImage" height="964" width="767">
    <g  class="vx-group vx-tree" transform="translate(20, 70)">
        <g class="vx-group" transform="translate(0, 70)">
            <g class="vx-group" transform="translate(0, 0)">
                <path class="vx-link-vertical" d="M451.5,0C451.5,233.5,451.5,233.5,451.5,467" percent="0.5" stroke="#f7f7f3" stroke-width="1" stroke-opacity="0.2" fill="none"></path>
            </g>
            <g class="vx-group" transform="translate(0, 0)">
                <g class="vx-group" transform="translate(451.5, 0)" opacity="1">
                    <g class="vx-group node__container" transform="translate(0, 0)">
                        <svg class="" x="0" y="0" style="overflow: visible;">
                            <polygon points="25.98076211353316,-14.999999999999998 25.98076211353316,14.999999999999998 1.83697019872103e-15,30 -25.98076211353316,14.999999999999998 -25.980762113533157,-15.000000000000004 -5.510910596163089e-15,-30" class="node__hexagon"></polygon>
                        </svg>
                        <g class="vx-group node__business-unit" transform="translate(0, 0)">
                            <use xlink:href="#icon-BusinessUnit"></use>
                        </g>
                        <g class="hierarchy-label__container" transform="translate(0, -40)">
                           <path class="" d="
                              M 0.0078125, 5.15625
                              L 34.64882865137755,25.156249999999996 
                              M -0.9921875, 5.15625 
                              L -34.63320365137754,25.156249999999996
                              H -65.8515625 
                              a8,8 0 0 1 -8,-8  
                              V -47.15625 
                              a8,8 0 0 1 8,-8 H 65.8515625 a8,8 0 0 1 8,8 
                              L 73.8515625, 17.156249999999996  
                              a8,8 0 0 1 -8,8 
                              L 34.64882865137755, 25.156249999999996 
                              Z 
                             "></path>
     			          <svg x="0" y="0" style="overflow: visible;">
     			              <text class="hierarchy-label__item__name" width="150" y="-25" x="0" text-anchor="middle" style="pointer-events: none;">
     			                  <tspan x="0" dy="0em">Finance</tspan>
     			              </text>
     			          </svg>
             			  <svg x="0" y="0" style="overflow: visible;">
             			      <text class="hierarchy-label__item__type" width="150" y="-5" x="0" text-anchor="middle" style="pointer-events: none;">
             			          <tspan x="0" dy="0.71em">Business Unit</tspan>
             			      </text>
             			  </svg>
                       </g>
                   </g>
               </g>
           </g>
       </g>
   </g>
   </svg>
</div>

Math:

enter image description here

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