Short for "Ma De Zhi Zhang" which means "fucking retarded" in Chinese. It's usually used to judge those who have done something really stupid or annoying.
1. The naked emperor is showing off his new clothes.
2. A man is complaining loudly that the plane took off (on time) without waiting for him.
Both you can say, "MDZZ".
This is an abbreviation of a Chinese word, "Ma De Zhi Zhang", or pronounced as "Mad The Zee Zhang". People use the word to express their anger or despise. Can be used in any conversations.