I choose nature to complement a Pokemon strongest stat and the moves I want to use.
Zorua has a strong spec attack and you plan to use Spec Attack moves.
So Timid is a good choice.
Newly hatched offspring don't have much variation in stats.
Sometime a different nature will make a 1 point change.
IVs are considered hidden because you have no idea what a pokemon's IV is unless you take it to the Judge or use an IV calculator. Most calculators aren't accurate until you get a Pokemon up to level 50 or so. There are a few ways to to see a Pokemon at level 50 without actually leveling it up