I installed version 0171 on my PSP, and it wouldn't run at all. The PSP would simply crash. Version 161 ran fine. So I unzipped the core_0171 file, and then it worked fine. But then I had another problem: certain specific sets of images were missing, even though they looked fine before. I read Wololo's suggestion that zip files must be in "store" or "zero compression" mode. I have no idea how to do that. So instead of figuring all this out, I went the easy route and unzipped them all. And now I can see all my pics.
It got me thinking though - is there really any good purpose behind zipping the files, other than making it faster to initially transfer them to the PSP? If they are in "zero compression" then they won't save any file space, and it seems like the PSP would have to spend a little extra computing power to get into the zipped folder. So, I guess what I'm really asking is, why zip them at all? Doesn't that just make the game run a little slower?