I know ph -> f is a common change from English to Spanish (or perhaps because the words share the Greek source).
Is x -> z a similar thing?
December 02 at 10:42
Not sure. I haven't seen it often enough to detect a pattern. In fact, this is the only example I have come across, though it might be true in very, very technical texts, which this is, and generally not available on Google. All the X words in English that I can think of off the top of my head begin with x in their Spanish translations, eg Xylophono, xenophobia.