Gundam part 1 is with the art box.
Gundam part 2 is with the art book.
Ultimate editon might be the only way they come together, but ultimate edition is 2 art boxes + a 3rd artbox housing those 2 +a hardback artbook and instead of the CE art books its a poster and some art cards.
Where they selling the gundam as seprate parts? it sound like as a bundle. but I have noticed some animes they put complete series for just part 1 (and gundam is one of those where this happens) (I assume its partly cause the titles naming from publishers can be a bit confusing (as in complete series for when the 1st season is released or in gundams case no actual identify just and episode count of 1-25))
Nadia 4k I think orginally when I bought from AllTheaAnime came with a loose extra/replacement disc, I can't remember the error, it might have been subtitles, so might be ok if your ok with dubs.
EDIT: This looks to be the ultimate edition, But I think it comes with an A4 hardback art book (well i think its hardback), which I would think Cex are very unlikley to take in and combine (certainly won't be required)
They also released a 4k part 1 & 2 and part 1 had the art box, part 2 I think is just case and discs and seprately sold