I've only played Ziggs a few times on his free week so I'm no pro with him, but I see a bunch of things in this guide I don't like (No offence intended).
1. Your glyphs: I'm not saying AP/per level runes dont work, but you would be MUCH better off with flat AP, runes are for early game after all.
2. Your first big item is Rabadons: This one I have a big problem with, you do get a RoA in your build and I did read the part about you sometimes getting it first,
but "70% of the time" not until second? RoA should always be one of your first items (if its in a build), in fact, the whole reason it's called Rod of AGES is because much like cheese and wine it gets better with time,
that being said it gives a decent chuck of AP, in addition to health and mana (you know the stuff that lets you do fun things like cast spells, and be alive). There is absolutely NO reason to not get this before Rabadons.
3. You start Dorans: This one is more of a personal preference of mine, but a problem I have none the less,
Dorans is a great Item don't get me wrong, and stacking them in a game is not a bad early game strategy but, starting with one is not great.
Dorans Ring gives you bonus health, but no way of getting it back. I think you will find 'Item + X Pots' superior in most cases.
All in all not a bad guide and decently written, but I think the build needs work in these 3 places,
and thus is my critique of your Guide