My understanding is images and animations are now compressed as much as they can be compressed. Further compression would make image quality noticeably worse.
I do not know what compression method or methods are used now, original poster proposes using compressors like AVIF and WebP, but maybe those are already in use?
To solve this properly would require testing available image compressors and measuring which makes smallest file size without making image quality worse. This would need testing on the HH images, they are not typical photographs.