depends what I'm doing. I get pretty descript with Z's, 7's and the like when calculusing
I also have to make a pretty concerted effort to distinguish my 5's from my S's
I've always crossed my 7's and Z's. Never my 0's, though. Maybe I should, though I hardly write 0's on paper, these days. Usually I type everything I need.
If you have to cross your 7s in order to distinguish them, you need to write better.
I don't cross Zs or 0s either, but at least I can see a basis for that.
I don't cross my sevens, but I cross my Zs.
I also like to actually draw the little hat on the 'a', like it has when you type it. See!
I cross zeroes when doing certain maths. C + s*cos(0) can get confusing when written out.
I don't cross 7's, but I do cross Z's. Otherwise they kinda look like 2's.