I'm Croatian citizen visiting Hong Kong and willing to visit Shenzhen as a part of my shopping tour

I'm Croatian citizen visiting Hong Kong and willing to visit Shenzhen as a part of my shopping tour. I understand that there is no firm immigration rules for that short time Visa permits as it is in ther hands of immigration officers on the ground. May I have your swift comment or reccomendation?

Many thanks and Best regards,

Robert Rajtić