@z ending nounbases

The z श्-ending nounbases, when not padafinal, work like normal consonant nounbases —

/diz- f + /jas OR /zas → !**dizas दिशस् "the four cardinal directions"

**divispRz- दिविस्पृश् mf + /jas OR /zas → !**divispRzas दिविस्पृशस् "skyscrapers"

as in

dizaz cAnavalokayan दिशश्चानवलोकयन् "and without looking far away" BHG 6:13

When padafinal, however, they get D ड् replacement by vrazcabhrasjas... and jhalAJjazonte —

Iz- ईश् + /su
→ Iz ईश् by halGyAbbhyodIrgh...
→ IS ईष् by vrazcabhrasjas...
→ ID ईड् by jhalAJjazonte
→ !**IT ईट्, normalizing

/pari + vraz व्रश् → parivrAD परिव्राड् → **parivrAT परिव्राट्

viz- विश् f "house" + /su
→ viz विश् by halGyAbbhyodIrgh...
→ viS विष् by vrazcabhrasjas...
→ viD विड् by jhalAJjazonte
→ !**viT विट् "house", normalizing

viz- विश् f "house" + /sup'
→ viDh विढ्
→ viksu विक्सु by SaDhoHkassi
→ !**vikSu विक्षु "in houses" with /Satvam

Yet, there are more exceptions than examples of that — most z-enders are rootnouns and get k क् replacement when padafinal. Grammarians explain that by saying that the root got /kvip affix. This makes kvinpratyayasy... turn z श् into kh ख्. Then jhalAJjazonte turns the kh ख् into g ग् —

/diz- + /su
→ diz दिश् by halGyAbbhyodIrgh...
→ dikh दिख् by kvinpratyayasy...
→ dig दिग् by jhalAJjazonte
→ !**dik दिक्, normalizing

/diz- + /bhis → dig- दिग् + /bhis, like above → !**digbhis दिग्भिस्

/diz- + /sup' → dig- दिग् + /sup', like above → dik- दिक् + /sup' by kharica → dikSu दिक्षु with /Satvam → !**dikSu दिक्षु "in the quarters"

**divispRz- दिविस्पृश् + /su → **divispRk दिविस्पृक् "skyscraper"

Many sucky wordlists list only diz दिश् or only dik दिक्, which is annoying. Use a serious dictionary like MMW when looking up short words. They warn you that /diz- together with /su makes **dik दिक्.