What is the meaning of ?

The hiragana syllable (zo). Its equivalent in katakana is (zo).

a particle used at the end of sentences, which indicates certainty, emphasis or even a warning or a threat.

a particle used as a suffix to an interrogative word to mark it indefinite.

a particle which makes a question emphasized or rhetorical, used at the end of a sentence or appended to an interrogative word.

topic particle used for emphasis

Source: wiktionary.org