To start, Ziggs cannot "one shot" towers. Nobody can. However...
It's silly that Ziggs can kill towers much faster than anybody else, but there are reasons to it that aren't exactly his fault. The Magic Damage done to towers from people who build AP is rather high (I think?) and Ziggs uses that along side his passive that gives him a basic attack that deals bonus magic damage. The next item on the list would be Sheen and Lich Bane doing bonus damage to towers, something that you might think would have gone away with Trundle's bite affect towers. The part that is a part of Ziggs' build is his Satchel Charge that blows up towers at 25% health from the first upgrade. I personally never liked this idea and now that the marksman is out of meta, Ziggs can finally use it to the full potential.
If your idea of "one shot" is being able to kill a tower with a single hit of an attack with no assistance, even if the tower has already had the health reduced, then yes, anybody can one shot a tower that was dropped to 10 health.
My recommendation would be to figure out a way to punish somebody for bringing a mage into the bot lane, even if that means bringing a mage yourself. The meta shifts and changes, this is a very drastic one in a short period of time, but maybe we will find mages going bottom lane and Marksman reworked to go mid lane? Who knows?
