Done a million times, but just in case you needed more Z9 w Z 100-400 sample images with hummingbirds. I haven't really done bird photos other than buzzards or Kites before (and even then they were perched.) We've had these feeders going for ages so thought I'd finally take the opportunity to try for some hummingbirds. These are from 400mm and 200mm. The background is about 50 feet behind the bird. No processing other than import to Capture One 22, crop, and export as JPG.

ISO 800, 1/2500, f5.6, 400mm

ISO 800, 1/2500, f5, 200mm

Here's an uncropped shot at 800 with the TC 2x to give you some more info, though the light was bad on the bird itself this is the go to spot while he guards his feeder. Had a hard time picking the bird up among bare oak branches, but got it after a couple tries with the Wide Area Small AF.

800mm, 1/250, f11, ISO 800