The /ʒ/ sound is spelled with <ge> in words of French origin or <su> in measure and treasure. The /m/ sound is spelled with <m>.
This is a contrast between a voiceless fricative and a voiced affricate, widely separated in the mouth. It is not a problem.
Since there is a huge discrepancy between the common /m/ sound and the rare /ʒ/, the mean density value is very low at 0.1%. The lists make 6 semantic distinctions, a loading of 60%.
Bruges broom luge loom measurable memorable measurably memorably rouge rheum rouge room rouged roomed rouging rooming treasure tremor treasures tremors
John Higgins, Shaftesbury, December 2010.