Likely released first as part of a "Crossover Classics Collector's Set," which also included Batman vs. the Incredible Hulk (Marvel; DC, 1995 series) and a preview of DC versus Marvel / Marvel versus DC (DC, 1996 series). This set likely shipped in late 1995, as the first issue of DC versus Marvel shipped in December of 1995.
Then likely released individually April or May 1996. Mike's Amazing World website lists the Previews solicitation release date of April 17, 1996. Comiclist.com lists an actual shipping date of May 1, 1996.