CEI 31-35 does not define zones (that is CEI 31-30 which covers classification). However, CEI 31-35 tells you which equipment fits which zone.
This covers identical technical content. cei 31-35 pdf
By adopting and following the CEI 31-35 standard, we can ensure that electrical installations are safe, efficient, and reliable, and that they meet the necessary performance requirements. CEI 31-35 does not define zones (that is
: Even if you're not in Italy, your country's standards body might have a copy or be able to direct you to where you can find the CEI 31-35 standard. cei 31-35 pdf