Salamun Alaikum.
They are completely different words.
‘Basir’ means all-seeing, having sight, knowledge or perception of something. See how ‘basir’ is generally understood in 12:93.
The meaning of the derivatives of ‘Zun’ depends on context. It can mean doubt, suspect, conjecture (45:32, 53:23, 53:28) It can also sometimes mean to ‘know’, to be certain about something (10:24, 18:53, 21:87, 38:24, 75:28).
Even in English we have ‘contronyms’ or ‘auto-antonyms’ which are the same words which carry opposite meanings depending on context. Such as:
Apparent – it can mean something which may not be fact and something which is ‘obvious’
Strike – In baseball, it can mean to strike the ball or it can mean to ‘miss the ball’
Overlook – Can mean to inspect something and can also mean to completely miss something.
Dust – To add small particles or to remove them
Flog – To keep promoting something or to beat or criticise something.
The Quran was simply revealed in a language that a certain people spoke with all their peculiarities. It spoke to them in their language. The Quran was not revealed in a new language.
I hope that helps, God willing.
Joseph.