I’m not sure how good rendering support is, but you can try explicitly specifying in Unicode that you want a zero with a "combining long solidus overlay": 0̸

I’m not sure how good rendering support is, but you can try explicitly specifying in Unicode that you want a zero with a "combining long solidus overlay": 0̸ (May render as 0 ̸, but should look like a single slashed zero. Wikipedia seems to think this is the way to get a slashed zero in Unicode: https://en.wikipedia.org/wiki/Slashed_zero https://en.wikipedia.org/wiki/Slashed_zero)