Dont plug your amp straight into the soundcards line in, or any inputs. You need to have some sort of balancing device in between, as the output from the amp may damage the inputs on the soundcard.

Also, the amps headphone jack is not an adequate output source, it doesnt sound nearly as good.

As for the current thing, sounds like something isnt ground properly, most likely the Zoom, altho i dont know how zooms behave. (is it/can they run on batterirs? if so use an adapter and make sure the ground is functioning properly)

If your really interested in recoring to PC, buy a Line 6 POD which is designed for that task.