Garza Zol is only good if it draws you a counterspell, but you only run four Force and four Drain/Leak to begin with, one of which was probably in your hand to defend Oath, and more of which were probably used up in the process of finding Oath and Orchard to begin with. Sure, you could draw a counterspell and just blow your opponent out - but more than likely, you'll draw a Chalice, or a land, or something else irrelevant, and you just gave your opponent an extra turn to wreck you. In my opinion, it's just not worth it.
If it were simply a matter of trading card for card with your opponent, it would be arguable that Garza Zol was better, depending on the density of cards your opponent could draw that scare you vs. cards you could draw that would stop scary things your opponent did. The problem, though, is that they don't just get an extra card, they get an extra untap step too.
I could see it in a more comboish Oath, like the Krosan Reclamation play mentioned, or one that plays, say, Mystical Tutor, Vampiric Tutor, and Regrowth, so that you could aggressively search out Time Walk after Oathing, depending on what ended up in your graveyard, but in builds like ICBM I think the extra untap breaks the camel's back.
