Author here, I mix up American and British English all the time. It's pretty common for us Brits to do that imo.
See also how all (?) Brits pronounce Gen Z in the American way (ie zee, not zed).
Sorry but it's highly suspect to be spelling the same word multiple different ways across paragraphs. You switch between using centre/center or utilization/utilisation? It is a very weird mistake to make for a human.
Brit here… I say Gen Zed!