You need to keep part 1 and part 2 in same place. Then you unzip file 1 and it unzips 2 also automatically. No wonder you had problems when you tried to unzip them separately.
I'd suggest using compressed version anyway. There's no visible sign of images being poorer quality and it's on one file.
I'd suggest using compressed version anyway. There's no visible sign of images being poorer quality and it's on one file.