For the squeamish read no further...
But in the Bearded Dragon care manual, house flies can be healthy munchies. I have to find out if zapped ones are okay. I would think electrocuted would kill bacteria. MMMM popcorn flies...
I doubt that a zapper would kill the bacteria carried by house flies...zapping just spreads fly parts and the bacteria all over your counters.
Some societies do consider certain insects as edible. When I was in Thailand, a lot of the locals ate Rice Bugs, and many of the local restaurants had several varieties on their menu. I got drunk enough...ONCE...to try some.