ぢ and じ are pronounced exactly the same. From the wikipedia page for じ:
「じ」は「ぢ」と同じ発音であり、現代標準語では「じ」と「ぢ」を音の上で区別しない。
“じ has the same pronunciation as ぢ, in modern, standard Japanese there is no distinction in the sounds.”
Likewise, all the combos are the same ぢゃ=じゃ、ぢゅ=じゅ、ぢょ=じょ. There is no “y” sound really in any of these; “ja”, “ju”, and “jo” are closer to the true pronunciation than “jya”, “jyu”, or “jyo”.
づ is different. “Dzu” matches pretty well though. Try saying “Ted Zoolander” really fast. Then ditch the “lander” and the “Te”. づ is about what you have left.