Complex sentence: The Swiss digital signing standard ZertES has defined a comparable concept of certificate service providers which need to be audited by conformity assessment bodies that have been appointed by the Schweizerische Akkreditierungsstelle.
Split into simpler sentences: The Swiss digital signing standard ZertES has defined a comparable concept of certificate service providers. They need to be audited by conformity assessment bodies that have been appointed by the Schweizerische Akkreditierungsstelle.