I put lines through my sevens and zeros only when next to other letters/numbers to differentiate them or to make them stand out. I do it as if it were a period to a sentence. Looks nicer anyways.
Closed 4s and not looped 2s. Open 4s and lopped 2s look sloppy as if the writer can't connect lines correctly. Reminds me of a kindergarteners closed fisted writing: sloppy.
Is the line through the Z a Canadian thing?