The first couple of Google hits for “Verzellung” (a noun “verzellt” could be derived from) are technical documents in German, so I think it is an actual word.
All instances of “verzellt” in those articles appear to be a spelling variant of “verzählt” (or rather “erzählt”). That’s either the third person singular form or the past participle of “erzählen”, viz. “to tell”.
“verzellen” seems to be a technical term used in relation to plastics, it is not a common german word. It seems to mean something similar to foamed, but slightly different. I googled a patent that explains “verzellt” as completely closed cells enclosed by evenly-thick walls.
After posting, I realised the correct term in English is “expanded” rather than “foamed”.
I have never seen the word “verzellt”. However I googled and found this text with numerous instances of the word, which allowed me to guess from context.