rustig sounds similar to rusty, so I'm just going to think of it as someone who is rusty with speaking
To me it sounds like rustic, I was imagining someone wearing old fashioned clothes.
I remember the word by thinking " hush, dig?" Which is USA slang for "quiet, understand?"
Careful: It's not necessarily about sound. Peaceful, calm, quiet, the opposite of busy, etc.
From the phrase/word "welterusten" (rest well/good night) I understand that the "rusten" part part is quite similar to "rustig". Rusten - rest, rustig - calm. It helps me remember anyway.
Why is "ze is rustig" wrong? What is the difference between 'ze' and 'zij'?
None, really, at least in meaning. The only difference is that zij is the stressed form (used for emphasis).
If you were doing a listening/dictation exercise, there's a difference in pronunciation:
The 'e' in ze sounds like the e in 'difference' (that sound is called a 'schwa').
The 'ij' sounds a bit like the 'ay' in 'May'.
Zij is to emphasise the pronoun. Like in English with 'the': you pronounce it "the" or to emphasise "thee"
"Zĳ" is the original form; "ze" is what you can say if the word is not important. Obviously, when the word is important, you can't get away with mumbling "ze", but you have to use the full "zĳ". The audio currently says "Zij is rustig.", without stress, but that's OK: No-one forces you not to say "zĳ". Except that the two forms don't sound the same, so if it's type what you hear, you have to write the right one.
But conversely there are a few other cases where it won't accept 'zij' for 'ze'
If you mean in Dutch, I can think of only one case: Discussing that eroded form itself. If you mean in Duolingo, I would say you should tell the editors to allow "zij" in those cases. But please, feel free to name any other examples.
I remember this because of this gif: https://31.media.tumblr.com/771c6cd3adaa06a01fdae292ab7a3510/tumblr_inline_mp0fhkCBaT1qz4rgp.gif. My people skills are rusty
"She is silent" didn't work. Not reported, as I'm not sure, how big the difference between being quiet and being silent might be and which is better represented by "rustig". Could somebody illuminate?
If someone overpowers me and puts tape across my mouth, I'm quiet. If I decide I'd better stop struggling and bide my time, then I'm calm. Only if I'm both of those, I'm "rustig".
Indeed, "rustiek" comes from French and before that from Latin and Italian; it refers to the country-side.
Really not understanding why zij is sometimes he, she, and they; but they aren't interchangable. how do you know when to use in context?
"Zij" (and "ze") can only mean she or they. He is always "hij".
In the sentence "Zij is rustig", you know "zij" means she because of the way "zijn" was conjugated: "is". If "zij" had meant they, then the sentence would have been: "Zij zijn rustig."