Boris Zvorykin was a Russian illustrator active at the end of the 19th century and the early part of the 20th. Apart from that, I’ve found very little background or biographical information. I would be curious to know, in particular, the relationship between Zvorykin and Ivan Bilibin, who also did colorful and decorative illustrations of Russian folk tales..
The best selection of Zvorykin’s work I’ve found is on the website of the Metropolitan Museum of Art, which counts at least 18 originals in its collection (and from which I’ve excerpted the images above).
These are done in gouache with metallic inks and black ink. The image portions of the sheets are roughly 11×8 inches (28x21cm).