A quick way to say โgood morningโ is zวo (ๆฉ), which literally means โearly.โ
A fuller expression is zวoshang hวo (ๆฉไธๅฅฝ), which literally translates to โgood morning.โ Zวoshang (ๆฉไธ) means โmorning,โ while hวo (ๅฅฝ) means โgood.โ
You can also say ย ๆฉๅฎ (zวo ฤn). Theย ๅฎ means peaceful, so you are essentially wishing that the other person has a peaceful morning.
In China (at least in Beijing, where I live),ย ๆฉ (zวo) by itself is probably most common, followed byย ๆฉๅฎ (zวo ฤn). It is more rare that people will sayย ๆฉไธๅฅฝ (zวoshang hวo),ย but all three are correct. If you are addressing someone, you usually say their name or title first. For example, ่ๅธๆฉ (lวoshฤซ zวo), which means teacher (่ๅธ (lวoshฤซ)) good morning.