Assuming all IVs are 31 on Zapdos, your Zapdos reaches these stats with your current EV spread and nature of Bold 252 HP/42 Def/216 SpDef:
Sp. Defence: 270
Now, if you switch to Calm, you can invest only 120 SpDef EVs to reach that same 270 SpDef stat. 124 Def EVs then brings you to that same Defence stat of 237. So what does this mean?
Calm 252 HP/124 Def/120 SpDef
Those EVs yield the same stats that you currently have but leave you with 14 extra EVs to invest where you see fit. Hopefully this helps you be more successful.
It is definitely awesome to see another Porygon2 lead user. If you are going to drop Recover for a third attacking move, HP Fight hits Tyranitar, Weavile, Heatran, Blissey(lol), and Magnezone harder so it would definitely be something to consider. You really only miss out on hitting Bronzong, Metagross, Jirachi, and Obamasnow as hard but that definitely seems like a nice tradeoff in my mind.