The /ʒ/ sound is spelled with <ge> in words of French origin or <su> in leisured and <zu> in azure. The /n/ sound is spelled with <n> or <nn>.
This is a contrast between a fricative and a nasal continuant, both in the same region of the mouth and both voiced. It is not a problem.
Since there is a huge discrepancy between the common /n/ sound and the rare /ʒ/, the mean density value barely registers at well under 0.1%. The lists make 6 semantic distinctions, a loading of 86%.
azure anna azures annas beige bane leisured Leonard luge loon luges loonies rouge rune
John Higgins, Shaftesbury, December 2010.