"κοιτούν" is 3rd person plural. Could you use this instead of "κοιτάζουν"?
Yes :) EDIT: this one has many forms, actually:κοιτούν / κοιτάζουν/ κοιτούνε / κοιτάζουνε / κοιτάν / κοιτάνε
Actually, there are many verbs in Greek that have many forms in some persons. This one has a "peculiarity", though. The same verb has two distinct versions. There is κοιτάω-κοιτώ and there is κοιτάζω. So, all persons have at least two forms, and some (as the 3rd person plural above) has many more.