refactor(zcash): simplify unsupported PCZT helpers

diff --git a/rust/apps/zcash/src/lib.rs b/rust/apps/zcash/src/lib.rs
index 6e46d2b..a0a97ff 100644
--- a/rust/apps/zcash/src/lib.rs
+++ b/rust/apps/zcash/src/lib.rs
@@ -188,7 +188,7 @@ pub fn check_pczt_multi_coins<P: consensus::Parameters>(
     // FUTURE(omitted-field-recompute): recompute-or-check omitted fields here,
     // mutating `pczt` so the normalized bytes carry the verified values forward.
     // transparent-only build: pczt's orchard feature (and resolve_fields) is not compiled here.
-    reject_legacy_check_unsupported_pczt(&pczt)?;
+    reject_unsupported_pczt(&pczt)?;
     let account_pubkey = transparent_account_pubkey_from_xpub(xpub)?;
     let account_index = zip32::AccountId::try_from(account_index)
         .map_err(|_e| ZcashError::InvalidDataError("invalid account index".to_string()))?;
@@ -230,7 +230,7 @@ fn transparent_account_pubkey_from_xpub(
 }
 
 #[cfg(feature = "multi_coins")]
-fn reject_legacy_check_unsupported_pczt(pczt: &Pczt) -> Result<()> {
+fn reject_unsupported_pczt(pczt: &Pczt) -> Result<()> {
     {
         // The legacy multi-coins check path only verifies transparent data. Reject any
         // shielded (Sapling/Orchard/Ironwood) or V6 PCZT so check, parse, and sign
diff --git a/rust/apps/zcash/src/pczt/parse.rs b/rust/apps/zcash/src/pczt/parse.rs
index 26d87d0..26a1084 100644
--- a/rust/apps/zcash/src/pczt/parse.rs
+++ b/rust/apps/zcash/src/pczt/parse.rs
@@ -395,7 +395,7 @@ pub fn parse_pczt_multi_coins<P: consensus::Parameters>(
     pczt: &Pczt,
 ) -> Result<ParsedPczt, ZcashError> {
     super::validate_supported_pczt(pczt)?;
-    reject_legacy_parse_unsupported_pczt(pczt)?;
+    reject_unsupported_pczt(pczt)?;
 
     let mut parsed_transparent = None;
 
@@ -430,7 +430,7 @@ pub fn parse_pczt_multi_coins<P: consensus::Parameters>(
 }
 
 #[cfg(feature = "multi_coins")]
-fn reject_legacy_parse_unsupported_pczt(pczt: &Pczt) -> Result<(), ZcashError> {
+fn reject_unsupported_pczt(pczt: &Pczt) -> Result<(), ZcashError> {
     {
         // The legacy multi-coins parser only displays transparent data. Reject any
         // shielded (Sapling/Orchard/Ironwood) or V6 PCZT instead of showing an
diff --git a/rust/apps/zcash/src/pczt/sign.rs b/rust/apps/zcash/src/pczt/sign.rs
index 023c862..a48190c 100644
--- a/rust/apps/zcash/src/pczt/sign.rs
+++ b/rust/apps/zcash/src/pczt/sign.rs
@@ -83,7 +83,7 @@ impl PcztSigner for SeedSigner<'_> {
 #[cfg(not(feature = "cypherpunk"))]
 pub fn sign_pczt(pczt: Pczt, seed: &[u8]) -> crate::Result<Vec<u8>> {
     super::validate_supported_pczt(&pczt)?;
-    reject_legacy_unsupported_pczt(&pczt)?;
+    reject_unsupported_pczt(&pczt)?;
 
     let signer = low_level_signer::Signer::new(pczt);
 
@@ -97,7 +97,7 @@ pub fn sign_pczt(pczt: Pczt, seed: &[u8]) -> crate::Result<Vec<u8>> {
 }
 
 #[cfg(not(feature = "cypherpunk"))]
-fn reject_legacy_unsupported_pczt(pczt: &Pczt) -> Result<(), ZcashError> {
+fn reject_unsupported_pczt(pczt: &Pczt) -> Result<(), ZcashError> {
     {
         // The legacy helper below carries the pre-NU6.3 transparent sighash implementation.
         // It must not be used for shielded (Sapling/Orchard/Ironwood) or V6 PCZTs.