How do you spell the Italian food ziti in Chinese? Mandarin Chinese? Standard Chinese, Standard Mandarin Chinese?

Phonetically in Mandarin it's 奇蒂 (Pinyin: "qí-dì").

There is no special word for "Ziti".

Most Chinese would just call it : 水管面 "shuiguanmian" (water pipe noodle)

This refers to any type of tube pasta (penne, macaroni, rigatoni, ziti...)

Here in Taiwan, I think ziti is long and tube-shaped, but slightly curved with a smooth surface, and we call it 意大利通心麵：
Wades-Gilos： i　ta　li　t'ung　hsin　mien　
Hauyu Pinyin：yi　da　li　tong　xin　mian

P.S. Oh, here in Taiwan, lots of Italian restaurants call this noodle
斜管麵
Wades-Gilos: hsieh　kuan　mien　
Hauyu Pinyin: xie　guan　mian
It sounds nicer than 水管麵 thought it indeed like a water pipe