Change CSS properties on click

Try this:

CSS

.style1{
    background-color:red;
    color:white;
    font-size:44px;
}

HTML

<div id="foo">hello world!</div>
<img src="zoom.png" onclick="myFunction()" />

Javascript

function myFunction()
{
    document.getElementById('foo').setAttribute("class", "style1");
}

Firstly, using on* attributes to add event handlers is a very outdated way of achieving what you want. As you've tagged your question with jQuery, here's a jQuery implementation:

<div id="foo">hello world!</div>
<img src="zoom.png" id="image" />

$('#image').click(function() {
    $('#foo').css({
        'background-color': 'red',
        'color': 'white',
        'font-size': '44px'
    });
});

A more efficient method is to put those styles into a class, and then add that class onclick, like this:

$('#image').click(function() {
  $('#foo').addClass('myClass');
});

.myClass {
  background-color: red;
  color: white;
  font-size: 44px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div id="foo">hello world!</div>
<img src="https://i.imgur.com/9zbkKVz.png?1" id="image" />

Here's a plain Javascript implementation of the above for those who require it:

document.querySelector('#image').addEventListener('click', () => {
  document.querySelector('#foo').classList.add('myClass');
}); 

.myClass {
  background-color: red;
  color: white;
  font-size: 44px;
}

<div id="foo">hello world!</div>
<img src="https://i.imgur.com/9zbkKVz.png?1" id="image" />