For Calm Zapdos, 20 Atk/30 Def (31 in the rest) nets you HP Ice with 68 base power.
For Modest Zapdos, 10 Atk/30 Def (31 in the rest) nets you 70 base power HP Ice.
Any other nature just ask. It's not really that hard to figure out. On shoddy, all you do is change it to the HP value you want, and then find a stat that is knocked down to thirty (try to use the one that is the most irrelevant to the set, so try not to knock down defenses). Then, substract four from that until the IVs work.
For example, start with 30 Atk Zapdos and go to 26, then 22, and continue that pattern until it works. You'll get 70 base power hidden powers with the same type. If none of those work (like with Calm Zapdos), then try the numbers in between (like 28 and 24). those give you the same hidden power type with 68 base power.
EDIT: At least it always works for me lol