Green’s Dictionary of Slang

zot n.1

[SE zero + ? squat n.2 ]

(US campus) zero, e.g. as in an examination.

[US]Poston & Stillman ‘Notes on Campus Vocabulary’ in AS XL:3 195: He didn’t get zot on that exam.
[Can]M. Atwood Cat’s Eye (1989) 88: We’ve known each other since the year zot; at my age, our age, that’s becoming important.