You can do anything you wish, but I would imagine this meeting will have consequences regarding your relationship with said managers. What you have to ask yourself is what exactly you're hoping to accomplish.
I don't expect their boss to side with a mere employee over both his managers, because - generally speaking - if he disagreed with their modus operandum to that extent he wouldn't keep them around.
Furthermore, if they're doing something "wrong" their bad behavior would reflect badly on him, so he has more reasons to keep it quiet than simply agree with you and somehow "punish" them.
Frankly, this sort of going over people's heads is more likely to result in you being branded a trouble maker than anything else, but i don't know enough about the situation and politics of your company to give any other advice.