"How is work father?"
Translation:Habari za kazi baba?
They both essentially mean the same thing. Za and ya are both prepositions meaning of.
Habari za/ya asubuhi is literally translates into "What news of the morning?" but means "How is the morning".
A dictionary states:
-a is the invariable element, which combined with a prefix forms the various prepositions wa, ya, za, cha, la, pa, kwa, ??iwa. In meaning these all correspond generally to the English 'of,' and (with the noun following) to the Genitive Case in the classical languages, and include all such adjec- tival relations as ' belonging to, pro- ceeding from, consisting of, of the class or kind of, relating to, qualified by,'
Wikipedia says that ya is used with noun classes 4, 6, and 9. Za is used with noun class 10.