The /z/ sound is spelled with <z>, <s> or <se>. The /ʧ/ sound is spelled with <ch> or <tch>. A good many pairs arise from contrasting a word ending in -ch with a plural or 3rd-person inflection, which acounts for the relatively high semantic loading.
This is a contrast between a voiced alveolar sibilant and a voiceless alveolar affricate. Some learners, such as French or Greek speakers, may have a problem especially when the /ʧ/ sound is final.
The mean density value is 1.2%. The list makes 91 semantic distinctions, a loading of 73%.
A's H avows avouch belles belch bells belch bens bench biz bitch boars bortsch breeze breach breezes breaches breezing breaching breezed breached breezes breeches B's beach B's beech bees beach bees beech burrs birch busy bitchy busier bitchier busies bitches busiest bitchiest cleanse clench cleanses clenches cleansing clenching cleansed clenched cons conch cosies coaches cows couch dizzies ditches does Dutch E's each ease each fez fetch fezzes fetches fills filch Finns finch fins finch gnaws nautch gulls gulch harries Harwich has hatch his hitch horns haunch Huns hunch inns inch is itch lawns launch leas leach leas leech lees leach lees leech Mars March mills milch moos mooch mulls mulch parrs parch pars parch parse parch parses parches parsing parching pause porch pauses porches pawns paunch pleas pleach please pleach pleases pleaches pleasing pleaching pleased pleached pose poach poses poaches posing poaching posed poached poser poacher posers poachers P's peach puns punch purrs perch readies Redditch res retch rose roach roses roaches R's arch scores scorch screes screech sirs search sloughs slouch stars starch swiz switch T's teach tawse torch tawses torches teas teach tease teach teaser teacher teasers teachers teases teaches teasing teaching tees teach tens tench tors torch Tsar char Tsars chars vows vouch was watch wens wench whiz which whizzes witches whizzing witching whose hooch wrens wrench zap chap zapped chapped zapping chapping zaps chaps zees cheese zest chest zinc chink zip chip zipped chipped zipping chipping zips chips zoo chew zoos chews zoos choose
John Higgins, Shaftesbury, November 2010.