ToLarin[exp] substitutes \gamma^{\mu} \gamma^5 with -\frac{I}{6}\varepsilon^{\mu \nu \lambda \sigma } \gamma^{\nu } \gamma^{\lambda} \gamma^{\sigma }.
GAD[\[Mu], \[Nu]] . GA[5]
ToLarin[%]\gamma ^{\mu }.\gamma ^{\nu }.\bar{\gamma }^5
-\frac{1}{6} i \gamma ^{\mu }.\gamma ^{\text{du19}}.\gamma ^{\text{du20}}.\gamma ^{\text{du21}} \overset{\text{}}{\epsilon }^{\nu \;\text{du19}\;\text{du20}\;\text{du21}}