Haven't read all of it, just skimmed.
Haven't heard of zig-zag diet. Looks similar principles to just a re-feed type thing. Will be interesting to see how you get on. Will you be doing cardio too?
As for light weight and higher reps. FUK THAT.
The best thing to build muscle is the best thing to hold onto it while dieting. Seriously tell him to go do some reading on some physiology or something. Nob.