it's pretty pointless and archaic to cross out 7s and Zs
it just adds more time when writing.
nah i've seen lots of people cross Zs and 7s and it's really common in Europe
it does take a tiny bit more time but it adds clarity especially with math (1 vs 7, Z vs 2)
i don't cross or dot zeroes but some people do
there's also how you write 1s (line, line w/ roof, line w/ roof and serif), 8s (two circles, figure-eight starting from top w/ bar, starting from middle, etc), and 3s (Ʒ vs 3)