Using SQL Server native backup and Veritas Backup Exec to backup the database and transaction log on the same database
i suggest you to configure one of the two backups in copy only:
https://docs.microsoft.com/en-us/sql/relational-databases/backup-restore/copy-only-backups-sql-server?view=sql-server-ver15
It is not strictly disallowed to use two different backup solutions but it exists only one single chain of backup so restore would be a nightmare.
Better to do full and ltog backup with one solution and use the other solution for full backups with copy only option.