from Harold Newman's 1977 book, An Illustrated Dictionary of Glass
zanfirico (Italian). The present-day term used in Venice and Murano for vetro a retorti; the spelling used elsewhere in Italy is sanfirico.
vetro a retorti (Italian). Literally, glass with twists. A type of glass decorated with twisted threads of glass embedded in clear glass, ...
Latticino or latticinio ... Terms that have been often misused ... without regard to the Venetian usage of the terms. ... The two terms latticino and latticinio have been used in Venice and Murano to apply only to clear glass decorated with with embedded threads of glass ...usually white threads.
So from that, I deduce that zanfirico is simply (?) a modern term for the older latticino (or latticnio).
But, just for info, there is even more confusion on the use of those earlier Italian words when mixed with "filigree" (and "fiigrana" - for coloured threads), as often discussed by paperweight collectors! I have never heard "zanfirico" or "vetro a retorti" used in connection with paperweights but "latticino" (and latticinio) is used often. Filigree and filigrana are also regular terms used in a paperweight context for "grounds", "cushions" etc. made of latticino. In the sense of the definitions above, I suppose we could refer to paperweight usage of embedded white threads (latticino or filigree?) as "zanfirico", but thankfully, I don't think it has been done. :shock: