I can not remember very many words containing a Z in their spelling...But seemingly those words spelled with an S are now the alternative!
eg: cognisant ...Alternative spelling of cognizant.
I suppose it is down to the manufacturers of this educative literature to provide the meaning, whether these educators be artificial, extraterrestrial , subterranean, intelligent or otherwise....Just ask Google 👽
I hope you have a most excellent day... This is if 24 hours is still called a day? 😁😁