The spelling of /p/ is always either <p> or <pp>. The /z/ sound is spelled <s> in inflections, <se> after vowels, <z> initially and <ze>. Also note the unusual spelling of czar, which is also in the dictionary as tsar.
The contrast is between a voiceless stop and a voiced fricative, fairly well separated in the mouth. It is unlikely to be a problem.
The only pair involving a taboo word is bump/bums.
Interesting pairs include
The mean density value is 1.3%. The list makes 178 semantic distinctions, a loading of 80%. This rather high figure is explained by the fact that many of the contrasts in final position are between an uninflected form ending in –p or –pe or –mp and an inflected form ending in –s, which clearly cannot be further inflected.
ape A's Bacup bakers beep B's beep bees bump bums burp burrs camp cams cape K's carp cars catchup catchers chap Chas cheap cheese cheep cheese chump chums clamp clams coop coos coop coups Corp cause Corp caws Corp cores Corp corps cramp crams crêpe craze croup crews croup cruise croup cruse damp dams damp damns dampen damson dampens damsons dapple dazzle dappled dazzled dapples dazzles dappling dazzling dep Des deep D's dollop dollars dollop dolours dope does dope dohs dope doze doping dozing drape drays dupe dues fillip fillies gape gays gape gaze gaped gazed gaping gazing gawp gauze gawp gores grape grays grape graze grope grows gulp gulls hap has heap he's help hells hemp hems hip his hoop who's hoop whose hope hoes hope hose hoped hosed hoping hosing hump hums jape J's jape jays jeep G's keep keys keep quays lamp lambs lamp lams leap leas leap lees limp limbs limp limns lip Liz loop loos loop lose looping losing lope lows mope mows nape neighs Naples nasals neap knees nope nose nope knows op Oz P zee pa czar pah czar pap zap par czar pars czars parr czar parrs czars pea zee peas zees peal zeal pee zee pees zees peel zeal peep P's pen Zen pest zest Philip fillies pierrot zero pierrots zeros ping zing pinged zinged pinging zinging pings zings pink zinc pip zip pipped zipped pipping zipping pips zips pipe pies plump plumbs polyp polys pomp poms pone zone pones zones pooh zoo pope pose poppet posit poppets posits prep Pres primp prims pyre Zaire quip quiz quipping quizzing ramp rams rape raise raped raised raping raising rape rays rape raze raped razed raping razing rep res repent resent repented resented repenting resenting repents resents repine resign repined resigned repines resigns repining resigning report resort reported resorted reporting resorting reports resorts repp res ripe rise riper riser Ripon risen romp rhombs rope roes rope rose rope rows ropy rosy ropier rosier scarp scars scollop scholars seep C's seep seas seep sees seep seize seeping seizing shape chaise sharp shahs sheep she's skimp skims sleepy sleazy sleepier sleazier sleepiest sleaziest sloop slews slope sloes slope slows slump slums snappy snazzy snoop snooze snooping snoozing soap sews soap sows soup sous sump sums syrup sirrahs thump thumbs tope toes tope tows tramp trams tripe tries troop trews troop trues troupe trews troupe trues turnip tourneys type Thais type ties up us viper visor vipers visors wallop wallahs warp wars weep wees weep wheeze weeping wheezing whelp wells whip whiz whipping whizzing whoop who's whoop whose whop was wipe Y's wipe whys wipe wise wiper wiser yelp yells
John Higgins, Shaftesbury, January 2010.