How to implement Zoom in and Zoom out
Working with Images
Zooming is basically a simple paint-action. You scale the image different and paint the GUI-Part new. Pretty simple. There is no native command for this.
You can make the task simpler for you with the controls you are using. Don't make the zoom too fine. Better to start with some basic values like 25%, 50%, 75% 100%.
Also please think about Thread-Handling as the rendering will take time and your application might get stuck in that process.