In my understanding, the part of speech of a compound word is determined by its ultimate morpheme. (複合語の品詞は、後にくる語（形態素）の品詞によって定まります)
蒸す(V)＋暑い(Adj) → 蒸し暑い(Adj)
持つ(V)＋物(N) → 持ち物(N)
and a verb in its -ず form can be roughly treated as an adverb.
食事をたいらげた ate up a meal
食事を残らずたいらげた ate up a meal completely (without any bit of remain)
Here comes the question. I find compound words ending with verb-ず have a variety of 接続, none of them are used as an adverb, e.g.
知らずしらずのうちに (resembles noun＋の＋うち)
役立たずな人 (resembles 形容動詞＋な＋人)
恥知らず者 (resembles イ形容詞＋者)
How should I understand such a variety of 接続? and when to use which 接続?
- I saw the subtitle "役立たず共め" in an anime, saw there is an example sentence "恥知らずなことをする" in my dictionary, and therefore I came up this question.
- I found compound words ending with verb-ず pretty versatile; it can be an adverb (in 日本人を恥知らず呼ばわりする外国人を批判する), a na-adjective (in 恥知らずな噓をつく), or a noun I guess? (in 馬鹿で恥知らずの人間になる) These three sentences are found on the Internet.