Files (e.g., images) with umlauts in the filename (ä, ü, ß, etc.) will not load in the game.
no difference between unpacked or ZIP archives. what means "deflate compression"?
i tested zips, created with this command
for /d %%i in (*) do "C:\Program Files\7-Zip\7z.exe" a -tzip -mx=9 "%%i.zip" "%%i*" -scsUTF-8
(without "-mx=...", and with "-mx=0")
it makes no difference.

everywhere same "bug"... 3ds, switch and android.
only in windows it works for me (+ retroarch).

you could try it with the game "Die Reise ins All" for example.
https://rmarchiv.de/games/50

Gabry said, this problem at nintendo-switch-version is caused by ... :"That's a bug in Nintendos file system driver: It interprets everything as Shift-Jis (Japanese encoding) even when the filesystem has a different encoding."
but on Android is the same bug!
Windows is ok.
Retroarch on nintendo-switch with easyrpg-core has not this bug. but laggy sound bug^^

I could test easyrpg-player with wii or wiiu too

greetz