I hope I get this right. Natives please check !
kuuza - to sell
Ninauza meza. - I am selling the table(s)
Wanauza meza - They are selling the table(s)
Wanawake wanauza meza. - The women are selling the table(s)
familia inauza meza - the family is selling the table(s)
familia zinauza meza - the families are selling the table(s)
familia zinauza meza zao - the families are selling their tables
meza inauzwa - the table is being sold
meza zinauzwa - the tables are being sold
meza imeuzwa - the table has been sold
meza zimeuzwa - the tables have been sold
Wa- is only for people and animals.
The N is more or less an underlying phenomenon. It's a prenasalising consonant mutation that takes place when it can ... the only prenasalised consonants in Swahili however are:
Plosives: mb nd nj ng
Fricatives: mv nz
So if a word stem begins with b d j g or v or z, it will have n (or m for b and v). W becomes mb, l and r* both become nd**. Aside from that, there is no prefix.
Okay I am not sure if i am right but this is my understanding.
I saw an example " Taa inatengenezwa" In this case i = The object prefix referring to "Taa" na = Present tense tengenezwa = Passive form of tengeneza
Hence i think same rule applies here.
zinauzwa: here the "na" after zi shows present tense.
Hence you need to "is being" sold