Visa situation for going into HK from Shenzen and back

If you get a China work visa (Z visa) in Italy, then enter Mainland China and change it into a residence permit within 30 days after entry into China, the residence permit can be used a multiple entry visa during its validity, generally speaking, the residence permit is valid for 1 year, it can be regarded as a 1 year multiple entry visa, you can use it to exit Mainland, go to Hong Kong and return to Shenzhen. Italian passport holders don't need a visa to Hong Kong for 90 days.