Sorry not to be able to write in Spanish, but I only started learning yesterday.
In one of the first lessons, the couple (Berta and Alberta) pronounce the letter “Z” as ‘th’ in Ruiz and López.
However, when highlighting the yellow words and clicking on the speech button on the right hand side of the page the lady definitely pronounces the “Z” as S each time!
Z and C is pronounced like th in most of Spain except for some small corners. On the other hand, as far as I know, in all of Hispanoamerica it’s pronounced as S.
The google replay seems to be oriented at the New World standard called español neutro.
There are other variations in the pluricentric Spanish language, in grammar, usage, pronunciation. For example in Argentinaand Uruguay ll (double L) is pronounced SH, whereas in most other parts it’s Y as in yes.
There is no ‘right’ way. Don’t worry and listen to it all.
Thanks a lot Ress and TommyTrueTravel, a bit confusing to say the least, but I won’t let it bother me too much.
Your help was much appreciated though and I thank you both.