In this reference photo of a Kamaz truck (assuming you renamed Kamaz to Zamak in the game), you can see that the drivers eye level is just below the upper edge of the left side window. He should be able to see to his left.
http://www.offroadvehicle.ru/AZBUCAR/KamAZ/kamaz_6560%20400%208x8.jpg
At the very least, he is able to move his head around so he can see better, this is not possible in Arma so it's important that the viewport is at the right height to begin with.