I take it the -z- is pronounced like an /s/, or at least has begun to do so recently

No, the -z- is pronounced like a /z/ like in easy and zoo.
Is a Frenchman who migrates to the U.S. at the age of 12, who is fully educated there and spends the rest of his life and 70 years of writing-teaching life there still a 'Frenchman'?
( he's 104 years of age and his book is a lovely swan song written in the 1990s)

Link

The essay with the word above mentioned was translated from Polish. I do not blame the translator for making a mistake, but the correctors and anchor man for carelessness.