He had a finger injury which is why he missed the Pindi Test last week. I don't know how serious it is, so I suspect he will probably be fit for the ZIM Test. That being said, I think Nayeem is a superior spinner, whilst Miraz is the superior batter. I would like to see Miraz be a guy who averages around 30 with the bat and therefore could bat anywhere from 6 to 8, per team demands. I think Nayeem only has the ability to average late teens to 20 max with the bat, ie a genuine #8 or #9.
Here's a video of Nayeem vs Windies, granted they aren't good players of spin, but Nayeem has 2 main advantages over Miraz: he's about 7-8 inches taller and gets more bounce, and he also turns the ball more than Miraz (or any of the other BD spinners, Shakib included).
https://www.youtube.com/watch?v=ljYuPbgAGZA