The 32 layered .procreate files come in four separate zips, named by the pieces inside: 01-09, 10-17, 18-25 and 26-32. Each one is complete on its own, so there's nothing to join or merge and no 7-Zip needed: unzip each zip, and put everything in one folder if you want all 32 together.
“Archive is damaged” or it won't open? The download was interrupted. Download that zip again on a steady connection and check its size matches the download page.
Not enough space? Unzipping needs roughly twice the zip's size free (about 5 GB). Do one zip at a time and delete each one after unzipping.
Ever see files ending in .001, .002 or .z01 (from somewhere else, not this bundle)? Those are split archives: put every piece in one folder and open the first one with 7-Zip (Windows) or Keka (Mac), and it rebuilds the whole thing.