If you have a special detail in your instagram profilbild picture that you want to show off, Zoom can be a way to bring it closer to your followers.
Sometimes small details can get lost in a profile picture. By zooming you can make sure your followers can see everything clearly.
While zoom is a useful feature, it's important not to overdo it. Too much zoom can result in blurry or pixelated images, affecting quality. Use zoom judiciously to preserve image quality.
Zoom is usually more useful with profile pictures than featured pictures, as profile pictures are often displayed as thumbnails, so they should be appealing at first glance.