I thought that kazi was word class 9, and it should be kazi yako.
Yep, but it's used in plural (i.e. "your works/jobs/tasks") so that makes it class 10 in this instance.
But if it is plural, then it sould be used kazi yenu, shuld not it? from the answer i see that i'm wrong, but why?
Kazi yenu would pluralize "you"; kazi zako would be multiple tasks belonging to one person