These riddles... are stupid. Riddles of these kind are always stupid, but it's particularly stupid here because of the subject and tone. Zankyou no Terror demands to be taken seriously, but relies too much on a cliched and implausible plot device to drive the narrative.
Shibasaki's solution to the first riddle is pretty much all literary analysis. It wasn't a logical, objective answer at all. It's only one of many potential interpretations of the allegory of Oedipus. If 9 and 12 were real terrorists, and were only using the bombs to draw attention to some greater problem, they would not risk all their credibility on the off hand that someone managed to solve their riddle. Conveniently, the police station was empty, so their moral position as hacktivists (who are good), as opposed to extremists (who are bad) was preserved.
The second riddle had the same problem as the first. Except this time, the police manage to disable it with the help of Shibasaki, saving the occupants of the building (if any), and preventing further damage.
By the third riddle, it wasn't even a bomb anymore. 9 was just trolling the police at that point.
It's really amusing, and painful, watching Watanabe tiptoe around the ethical issues inherent in a story about terrorists. The "There were 27 injured, but they were all minor injuries," line in the second episode made me laugh in particular, bringing to mind the ridiculous parachutes in Legend of Korra that appeared every time a biplane exploded. By then, it was clear that Watanabe couldn't bear to have 9 and 12 actually kill people.
And yet, he still leans heavily on the allure of terrorism: the desperate acts of people betrayed and abandoned by the world. Unfortunately, he undermines this idea every time 9 and 12 succeed at a bombing without any significant consequences, particularly not consequences that might make the duo unsympathetic. He is either unaware of, or unwilling to address the reasons that make terrorism a compelling social phenomenon.
So, yeah, my problem with this show is that the writing is too cowardly. If it seems I'm holding Zankyou no Terror to unreasonable standards (in the context of anime), it's because I expect much more from someone with Watanabe's pedigree.
EDIT: Lol I forgot this was the Aldnoah thread.