After watching the ova again today i realised that some zoanoids were redrawn in other episodes but a few i could't recognise. I know that in the mangas there are loads of zoanoids we never see again, here is just two i found.

I'm pretty sure the red one is supposed to be Zerebuth but the purple one has always been a mystery. We saw a proto-Enyzme. About the only things that actually look like themselves are Guyver I, II (aside from shape) Gregole, Vamore and Ramoith. A best they had about one book to draw work from and that Zoanoid doesn't fit any datafile ones from the first book.

That purple one actually looks really cool, but definitely not very Zoanoid-like. There's a clear difference between what Takaya designed and what was designed by the OVA team. Including the brown Enzyme, they all seem to have very generic muscular bodies

yeah the purple one look like it belongs in the sea it seems to have a crablike or clam body amour.But the claws are awesome. 

Yeah, I watched the scene again and it's face looks squid-like. With the vertical mouth it reminds me a bit of Kadan, so maybe these designs were more influential than we might've thought

These were possible low quality redesigns of sketches and Guyver work from the Mangaka. The creatures and guyver in this OVA movie are by far the most organic we've seen... at least in the gross department. The Monster designs themselves were fairly simple with the exception of Vamor and Gregole. The undetailed designs were probably due to the budget constraints and fodder(redshirt) status. However, there is some clear influence from the manga. On the other hand, it's possible that Enzyme enzyme looking one inspired the Manga. It's really up in the air considering the lack of re-releases and production notes.