German mediatization 

In the second paragraph of the article on German mediatization, I see "secularization", spelled with a "z", and "secularised", spelled with an "s". Is that right? Shouldn't they be spelled the same, both with "z" or both with "s"? I notice that the title is "mediatization", with "z". I don't care either way; I just prefer consistency. What do you think?