How can quicktime record audio from two sources: mac and iphone?
Just setup two windows in QuickTime: one for iPhone video and audio, and the other for Mac audio and press record on both windows. If the Mac audio isn't synchronized perfectly with the iPhone audio and visual, then you can just use iMovie or Final Cut Pro X, if you have it, to edit them.

Make sure that "New Audio Recording", for your Mac's internal microphone, is selected FIRST, then create a new window by selecting "New Movie Recording", for iPhone video and audio. If you select "New Movie Recording" first, then "New Audio Recording" will be grayed out. I don't know why, seems pretty stupid.