Zip guns may get past a metal detector, but not the standard x-ray luggage scan. To the extent it'll make it past the x-ray screeners, it's because they let all kinds of stuff through, because it's a poor way to screen for dangerous things, and they are not high-skill employees, they are relatively cheap labor.
Source: I used to travel every week flying home Friday, cycle clothes out of my travel bags, and be on the road again on Sunday night. I learned to my horror I'd been flying with a pair of scissors for at least 5 weeks - during which, TSA forced me to open a Christmas present for my sister and throw away some hand lotion which was in too big of a bottle.
There's a reason they call it security theater. This is just more of it.
