Thought I'd throw in my two cents since I'm Polish - here, the name is seen as elderly sounding, and most Zbigniews are over 50 and go by Zbyszek. I don't think it suits a child and I dislike the sound.
masculine list:
https://www.behindthename.com/pnl/191050/124079feminine list:
https://www.behindthename.com/pnl/191050/124080