A friend of mine's just made the typographics of a name which includes
the word "liz". He's chosen a z-letter which loods most similar to the
numeral "3". I said him that people who don't come from a German
country might not be able to read this. But I'm not sure about this.

I believe the z-letter which looks like the numeral 3 (with the upper part
of it in n-height) is a relict from the old German current hand, which is
developped from the "broken" scripts, or Gothic scripts (I think "Gothic"
is what they're called in English), e.g. the fractura or the schwabacher.
When I was in school in Germany, we didn't use this 3-shaped z-letter at
all, but in Swiss schools it's the standard form of the z-letter in current
writing, even though of course the current writing is developped from an
antiqua.

Are there other places where that 3-shaped z-letter is still in use? Would
people be able to read it?

xeeniseit