I think I’m naming a character [name_m]Zygmunt[/name_m] “Zyggie” but the only reason I’m hesitant about it is because I don’t like Zyggie. I don’t know why, I just never have, but I need something positive to be told me about Zyggie so I can name him this and not resent it every time I write his name*.
So, sell away!
(*I’m like almost completely sure that this is his name so I don’t think I’m open to just naming him something else)
It has rarely used letters and rhymes with … piggy?
Umm sounds very animated?
I agree, it’s unique! It stands out and it will help your book be more recognisable, than if you were to name all your characters basic, typical storybook names. It sounds very bright and cheery, a great contrast with the mysterious and elegant [name_m]Zygmunt[/name_m]. Kind of shows two sides of the character.
Zyggie is funky, cool and unexpected
It has some quirky, cool sounds
Its so cool and unique. Readers will probably associate the name with your book which helps it to stand out more.
Works great for a character! It has a lot of personality!
Zyggie is seriously funky! In the [name_u]Ziggy[/name_u] spelling, I love it as a nickname and would even use it as a first if I was a cool celebrity or something 
Very fun and energetic.
Also, [name_m]Zygmunt[/name_m] is great! [name_m]Sharp[/name_m], surprising and handsome.
I actually know a girl named [name_u]Ziggy[/name_u]! That’s all I can say, lol.
Zygote is chil. Oh flip it auto corrected to Zygote…what if you spelled it Zigi or [name_u]Ziggy[/name_u] or [name_m]Ziggie[/name_m] or [name_m]Zygi[/name_m]
It has a cool disco vibe and it’s fun to say. It’s also the name of my rumba though we spelled it [name_u]Ziggy[/name_u]
Zyggie has pop, but maybe Zyg is more in your wheelhouse its a bit less boyishly handsome yet still in the distinct sounding wheelhouse.
The spelling Zyggie really throws me off… I want to pronounce it similarly to Zygote…
I much rather the spelling of [name_u]Ziggy[/name_u]. Otherwise, I really like [name_u]Ziggy[/name_u] as a nn for [name_m]Sigmund[/name_m]/ [name_m]Zygmunt[/name_m]