Often followed by だ/だった/になった/で
ずじまい expresses that something ended up not being done, often with a sense of regret, disappointment, or missed opportunity. It conveys that the speaker intended or hoped to do something, but in the end it never happened. The nuance is close to "never got around to doing" or "ended up not doing" in English.
Attach ずじまい to the negative stem of a verb (the same form used with ず):
It is commonly followed by particles like だった, になった, or で to complete the sentence.
The key nuance of ずじまい is that the speaker had some intention or desire to do the action, but circumstances (time running out, lack of opportunity, procrastination, etc.) prevented it. This distinguishes it from simply stating that something didn't happen with ないで or なかった.
It often appears with expressions like けっきょく結局 (in the end), ついに (finally/never), and せっかく (even though one went to the trouble of) to reinforce the sense of a missed opportunity.