Thanks for posting the links! I'd seen them before, but forgot about looking there. You can't post scans here, but I'd love to see the pieces in the book. If you get a chance, could you email me an image or two? If there's text that talks about them I could translate it, too.
I wasn't familiar with Zach's work, but I've found several pieces on the internet. He doesn't seem to me in my Bohemian glass books, maybe because though he was born in Prague, by the time he was 20 he worked near Munich. There's an interesting interview with Reino Reike at the Victoria and Albert Museum about a goblet he engraved at
http://www.vam.ac.uk/collections/glass/audio/audio_proms_talk/index.html. Zach died in 1881, though, which seems to place him earlier than this was made. From the Zach pieces I've seen, his style was different than that on the goblet here, but I'd like to see a wider range of his work. Interestingly, the goblet at the V and Z looks sort of like it has a twisted colored thread in the stem, but it could be a bubble reflecting the blue layer. (Incidentally, Zach engraved a reproduction of the Portland Vase!)
The chunky, heavily cut feet I'm thinking of were made from about 1830 until at least 1880. Not all feet on pieces engraved in this style were like that, but even the plainer, round ones on the goblets in the links are quite heavy. Are those in your books are lighter?
It's interesting to think about the possibility that the goblet was engraved on the Continent based on an American image (or images), as Ms. Spillman suggested. That would almost certainly mean that it was made after 1902 because of the position of the chevron, unless for some reason it was deliberately inverted. That makes sense to me, too, considering the form and designs on the bowl and foot. The cut design on the bowl has always reminded me more of Art Nouveau stuff from Steinschonau than earlier work, but who was engraving in this style (and with this skill) then? Although as Kerri pointed out there were many engravers around, this piece is extremely well-executed. To get the detail evident here in colorless glass would be difficult enough, but to also get such precise shading in cased glass is pretty phenomenal. The detail on the horses' heads is astonishing. The red is very dark and shallow, so you get dramatic contrast with little change in depth.
I'd give a year of my life to own this goblet and be able to study it!