1. If you ever get a chance, pull out the flyback transformer from an old TV set or monitor. Real handy thing to just "have around." For all legal purposes, of course. Just don't break the damned CRT tube.
2. Regarding noise, a friend of mine borrowed a pump-up Crosman for defending his city garden against squirrels. I warned him about the noise attracting the ire of neighbors. When I saw him again later, he said one neighbor spotted him dispatching them and thanked him. His garden apparently became the neighborhood squirrel "sink."
3. I'd have put a wide-mouthed steeply sloped funnel under the squirrel zapper going into a squirrel-proof container to avoid sprinkling feed on the ground. Loved the musical background in that zapper one.
4. I couldn't quite tell how that squirrrelapult was triggered --manually?
5. Obligatory, in spite of OP's prohibition, and for all legal purposes, of course: