Question

If that is possible Machamp can ruin Shedinja:)

Comments

Almost anything can ruin shedinja. :/

Answer 1

No, No Guard does not allow you to attack Shedinja except with an attack that is super-effective.

Answer 2

I wouldn't be so sure... because it hits doesn't mean it affects the targeted pokemon, even if a machamp uses dynamic on a gengar and hits, does not mean it affects it.
you could for example use a fire punch to win over a shedinja but that has nothing to do with no guard ability