TL;DR: Multiple concatenated zip files with the following EOCD records (end of central directory)
```abcdefghijklmnopqrstuvwxyz{CTF0137}_TF0137}_F0137}_0137}_abcdefghijklmnopqrstuvwxyz{CTF0137}_CTF0137}_qrstuvwxyz{CTF0137}_137}_tuvwxyz{CTF0137}_}_nopqrstuvwxyz{CTF0137}_137}_efghijklmnopqrstuvwxyz{CTF0137}_7}_stuvwxyz{CTF0137}_opqrstuvwxyz{CTF0137}_
{CTF0137}_37}_qrstuvwxyz{CTF0137}__```The 0th is a dictionary, the other lines are substrings of it, encoding the letter before it, so `TF0137}_` -> C, `F0137}_` -> T...
[Full writeup](http://sigflag.at/blog/2022/writeup-googlectf2022-appnote/)