Formal:
* Natumai unafurahia likizo yako. (This is the most literal translation and quite formal.)
Informal:
* Natumai unapata raha kwenye likizo yako. (This is a more conversational way to say it, implying "having fun".)
* Natumai unapumzika vizuri kwenye likizo yako. (This emphasizes "relaxing" during the holiday.)
* Natumai unakaa vizuri kwenye likizo yako. (This translates to "I hope you are staying well on your holiday.")
More casual:
* Enjoy your holiday! (This is directly translated from English and is often used in informal contexts.)
* Likizo njema! (This means "Happy holiday!" and is a common greeting.)
You can choose the phrase that best suits your relationship with the person and the context of the conversation.