Zooming with AVCaptureDevice and AVCaptureSession

Zooming with AVCaptureDevice and AVCaptureSession

I have a photo app when I want to support zooming up to 4x without
pixelation. Currently I zoom by transforming the whole view:
previewImageView.transform = CGAffineTransformMakeScale(value, value);
This pixelates my image view, and is especially noticeable at my desired
max zoom (4x). Is there a way to get a higher res preview for zooming?
Currently I'm using AVCaptureSessionPresetHigh, but I want something up to
4x higher resolution. How do I get a high resolution preview?
Maybe I could use AVCaptureSessionPresetInputPriority could work? Any tips?
Or is there an easier, more performant way to do this within GPUImage?