A verbal agreement had been made and Zach didn't feel that it was necessary to get it in written as Clara seemed to be a trustworthy person and was unlikely to betray his trust.
Clara on the other hand had grown too suspicious of the force that Zach was leading. She had been out of the city on several occasions before this. Ever since she had been young, her family had insisted that she experience the world outside and its dangers. Therefore, she had met with several travelling merchants and caravans that never settled in one place for long. She found that those people were the most free spirited out of all the strange folks she had encountered. They were not even close to Zach's men in terms of discipline, strength, strategies and battle sense.
Therefore, Clara seriously doubted Zach's identity and that of his men. She even wondered if she was leading a group of wolves into her home.