Was it possible for queen Victoria to fasten her gown zipper?

No, because Queen Victoria died on 22 January 1901 and the modern zipper was not made until 1914.

(Gideon Sundback's invention of the "Hookless Fastener No. 2" in 1914 was the first version of the zipper without any major design flaws and essentially indistinguishable from modern zippers.)