There is no such a thing as zalgo characters. It is plain unicode (utf-8 shaped), in particular it is an abuse of combining characters. Disabling those can cripple non-english languages.
It's possible to look at how "overloaded" the combination characters are and trigger a filter if above a certain level.
I doubt non-english languages quite overload as much as "zalgo" generators.
I'm actually not sure where the term Zalgo comes from. I know the effect is abused Unicode feature, but was never sure how does the term "Zalgo" end up explaining it.