The Z is correct English.Check the OED. They seem to know.
(
DogHorse plop,
Thu 10 Aug 2006, 10:23,
archived)
yepi don't use -ize myself but i have no objection to it.
the arrogance of my fellow speakers of british english never fails to amuse me.
(the arrogance of my fellow speakers of british english never fails to amuse me.
urbane legend i have known the inexorable sadness of pencils,
Thu 10 Aug 2006, 10:36,
archived)