After reading the first 5 chapters, have the students (in groups) draw a picture of Zinkoff based on what they thnk he looks like. Tell the students to use information from the story. (There are no physical descriptions of Zinkoff at this point, but the students will have an idea as to what he looks like; encourage them to incorporate images, scenes, dialogues, etc.)
Periodically revisit the group drawings--make any changes necessary. While this activity isn't something to focus on, I think it's a good break from reading that will allow the students to work on visualization while also showing the character's motivations, traits, and so on.