Okay, the user wants me to translate "zig-zag" into Vietnamese. Let me check the rules again. The first rule says to translate all content into Vietnamese. The second rule states that if the content is already in Vietnamese, leave it as is. The third rule is to provide only the translation without explanations.
So, "zig-zag" is an English word. I need to find the correct Vietnamese equivalent. The common translation for "zig-zag" in Vietnamese is "zích zắc". I should confirm that there's no existing Vietnamese term that's already used. Since "zích zắc" is the standard translation, I'll use that. No need for explanations, just the translation. Let me make sure there's no typo. Yep, "zích zắc" is correct. Alright, that's the response.