There are thousands, here are a sampler:
Some Scrabble words that start with U are:upususeunderuncleurineuntoundounclearunnecessaryumbrellaurgentuglyusefulumberutilityunusualunguentuniversalupperundulyundecidedutmostunitunmanageable
Words starting with USHUsherUsheranceUsherancesUsherdomUsherdomsUsheredUsheressesUsheretteUsherettesUsheringUsheringsUsherlessUsherredUsherringUshersUshershipUsherships
Axe.
avenue??
effecteffigyefforteffuse
knowledge
crocus
There are no words that start with ZH, here are some words that start with z:ZacatonZaddickZaffarsZaffersZaffirsZaffresZaggingZaikaisZamarraZamarroZananasZandersZaniestZanyishZapateoZappersZappierZappingZaptiahZaptiehZarebasZareebaZaribasZealotsZealousZeatinsZebecksZebraicZebranoZebrassZebrineZebroidZecchinZechinsZedoaryZelkovaZemstvaZemstvoZenaidaZenanasZenithsZeoliteZephyrsZeppoleZeppoliZeroingZestersZestfulZestierZestilyZestingZeugmasZibethsZiggingZigzagsZikuratZilchesZillahsZillionZincateZincifyZincingZinciteZinckedZincoidZincousZinganiZinganoZingaraZingareZingariZingaroZingersZingierZingingZinkifyZinniasZiplessZiplockZippersZippierZippingZirconsZithernZithersZizzledZizzlesZlotiesZlotychZoarialZoariumZocalosZodiacsZoeciumZoisiteZombiesZombifyZonallyZonatedZonkingZonulaeZonularZonulasZonulesZooeciaZoogenyZoogleaZooidalZooiestZoologyZoomingZooningZootierZootomyZorillaZorilleZorilloZostersZouavesZoysiasZydecosZygomasZygosesZygosisZygotesZygoticZymasesZymogenZymosanZymosesZymosisZymoticZymurgyZyzzyva
Zigzag ? i think
reject
identify idiot
ivy and ivory