To put it bluntly, no, those are not good IVs. With a Pokemon like Zamazenta, it is necessary that you have max attack and speed, as a minimum. Your Zamazenta has only decent speed and attack. The only saving grace with this is its nature, adamant. As for making Zamazenta a special attacker, just don't. It's attack stat and movepool are far superior. I would recommend that you soft reset to try to get max attack, speed, and something other than special attack. Natures don't matter, as you can change them with mints.