I am confused regarding the letter ". Is it's proper arabic spelling زاء which will then be pronounced za' and not zay or zayn or other ways. Shukran Jazeelan

Question
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
ِAnswer
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. 
3fwaan
Wa assalaam alaikum