Zula 1

Ok. There was an actress Zula Pogorzelska (1898 - 1936). But her actual name was Zofia not Zuzanna. Besides in the time she lived it was popular to make out odd diminutives, it's a sign of the times. If you want to have Zula in your database you should also have other silly diminutives from 19th century Poland like Orcio from Jerzy, Zizi from Józefina, Żancia from Joanna, Ladi from Władysław, Zuta from... no one really knows what. They're not legitimate diminutives, it's just what fashionable parents used to like to call their children. What's more, sometimes it's really difficult to say what name did the diminutive derived from (e.g. I've heard of Zuzanna being called Zuta but my Polish literature teacher thinks it's from Kazimiera).
Why do you even bother to list Polish diminutives here? It's illegal to call children in Poland with diminutives. You must always call your child with a full name. And the form of diminutive is only limited by one's fantasy.
[this website does not limit itself to only listing legal names that go on birth certificates -ed]

In that case you have a lot to go with Polish names. Maybe you should at least limit it to those widely used and accepted diminutives. Because it's enough to add typical endings to any name to make a few pet forms. Even my name despite not being typically Polish has lots of diminutives. I don't think contributing them all would be a good idea.