>>5268373sadly there aren't really official lineart for the zoids themselves that I know of. However the manuals for the HMM kits tend to have a lot of lineart of the weapons, parts, etc. just check out hobby search/1999. But I am sure those aren't the line arts you mean, you want something for color tests don't you?
The older kits did have side view and top views of the models that were drawings for the painting guides, while newer ones use pictures of a painted kit. You could try and covert those drawings into line arts with a good deal of work.
Finally there is TONS of fan made lineart I have seen, but your mileage will HEAVILY vary on those.