iPad mini Display Zoom setting is missing?
In Display & Brightness, the option for display zoom is missing. You can find it listed in a Settings search but it is not there.
iPad mini (7th generation)
Display Zoom is only a feature on certain iPads and the iPad mini is not one of them:
Tip: To get more screen space to work in (on supported models), go to Settings > Display & Brightness, tap Display Zoom, then select More Space. This option increases the pixel density so you can view more content in your apps, which is useful when working in multiple windows in Stage Manager or Split View.
Move, resize, and organize windows with Stage Manager on iPad – Apple Support (MY)
If you see it by searching in Settings, it is likely a bug as it may be part of iPadOS, but not available on your model. You can send feedback to Apple here:
You should be able to use the Zoom option in Accessibility Settings: