This is the 446th most frequent Marathi word.
झप
A sudden, quick movement or action.
In this sentence, 'झपकन' means 'quickly', describing the manner of the action.
तू जर झपकन उडी मारली असती, तर चुकला नसता.
If you had leapt quickly, you wouldn't have missed.
Here, 'झपकन' emphasizes the swift action of glancing.
पुस्तकावर झपकन नजर फिरवलीस आणि तुला उत्तर सापडलं.
You glanced quickly over the book and found the answer.
'झपकन' is used to depict the rapidity of the movement here.