idx language code "zh" gets expanded to "zho", not recognized by tesseract

[Seegras]

I actually opened an issue there too: tesseract-ocr/tesseract#2995

$ grep id: subs-chi.idx
id: zh, index: 0
$ vobsub2srt subs-chi
Error opening data file /usr/share/tesseract-ocr/4.00/tessdata/zho.traineddata
Please make sure the TESSDATA_PREFIX environment variable is set to your "tessdata" directory.
Failed loading language 'zho'
Tesseract couldn't load any languages!
Failed to initialize tesseract (OCR).