How to get HQ zoom on saved photos?

How to get HQ zoomed in photos on pictures you already have saved?
I have a saved photo and I want to zoom in on a part and make it in HQ or nice enough to see well btw it's an iphone picture how can I do this because regular zooming makes it bad quality and you can't make it out like zoom zoom zoom in on the picture then like the pixels 'magically' become HQ or at least good

You can't. Stop asking.

What you need to do is to your "zooming" before you press the shutter release.

What you are calling "zooming" is actually cropping. When you crop an image, you end up with less data and that will reduce the resolution of your image.

In the future; * fill the frame of your camera with the image you want, * shoot in RAW or the highest resolution your camera supports, * minimize the amount of cropping is post production.

Since I already answered your question for you, I take it your methodology for gleaning information is to go around pestering everyone til you get the answer you want to hear. I will paste the answer I gave you earlier. Maybe this time you'll take the time to read it.

"Unless I'm sorely mistaken, at this point pretty much all cellphone cameras still rely on digital zoom as opposed to optical zooms. Digital doesn't really physically zoom in on anything. It just rearranges pixels on the view finder in order to "create" a zoomed in image. If you're trying to zoom in on a pre-existing photo, the quality will rely somewhat on the original quality of the photo. If the photo was low res to begin with, zooming in will make it look like a pointillist painting."

The more you crop (or zoom) into a photo, the more detail you will lose. Scientific fact, I'm afraid.