Yes, I do exactly as you write... bu my 7zip sw (x64 version, latest) doesn't show among the compression options, as first choice in the list, as your picture "0 - Nessuna" instead as first choice I have "Memorizzazione" (see my picture).My procedure is go into the folder, select the part0, part1 and desc.text.
Add to archive.
So what you do wrong is that you select the whole folder, you need to select the two folders part0, part 1 and desc.txt
Name it bootanimation.zip and see screenshot.
View attachment 5927045
Important I have other screen like you ??
But I think it's the same...
ITA : Memorizzazione = EN: Store
rather than using .png for the frames, better .jpg (so the final zip is "lighter" and perhaps faster OS cold boot?
Or same thing?