As-salaamu-alaykum and Shukran for the much needed service you provide.
I am confused regarding the letter ز;. Is it's proper ِrabic spelling زاء; which will then be pronounced za' and not zay or zayn or other ways. Shukran Jazeelan
Wa alaikum assalaam wa rahmatullahi wa barakaatuh
The letter ز is written as زاي when it is written out as a formal name. It is just a name though and doesn't change how it is pronounced when reciting the Qur'an.
The names of the Arabic letters often have more than one correct way of being written as a formal name of the letter.
Wa assalaam alaikum