Zach's bright orange hair, a famous trait of the Evandiels, was solid proof that he was who he claimed he was. As members of one of the duchies, the Systine guards naturally knew at least superficial information about the other duchies, including the Evandiels.
Then, there were the unfounded rumors regarding a certain young Evandiel causing a bunch of trouble at the Academy, the very same Academy as the one their young miss was attending. They had heard about him. They knew who he was.
That didn't mean they were going to help him just like that. They would have if it was anyone else.
But the guards had heard that Violina was pretty close to him from their sources at the Academy and the uncles Tayup and Krage.
When Violina and her insect-loved friend returned, they had also made quite a ruckus about leaving a third friend behind at the Labyrinth's entrance.
