I've learnt quite a bit about supply lines and geographical factoids from his two books, but I cannot imagine how a well-read and smart person would do the kind of overarching generic speculations that he does (probably trying to appeal to a certain, simple-minded, audience).
It has been apparent that he doesn't know much about most of the countries that he speculates about. The point about demographics in Israel is obvious and oft-repeated (but the decline of Ashkenazis who brought the scientific culture of the fin de siecle Central Europe to Israel is a much more dire crisis for Israel as is apparent from the decline of the quality of their human capital, both in propaganda and intelligence fronts, notwithstanding whatever "innovation index" or "startup ecosystem ranking" some retard or retards in suits come up with), but the rest is just mumbo-jumbo honestly.
He talks about U.S. intentions similar to "mommy's special" conspiracy theorists: as if U.S. is just this one very consistent and determined guy who makes 100 year plans, doesn't change them ever, is immune to the flux of the torrents of history, and omnipotent in applying this plan.
A realist will argue that an increasingly domineering China in East Asia will force an Asian pivot from U.S. whether they like it or not, but this attitude (carrying the unwarranted misnomer of "realism") is akin to the incapacity of rational agent theory of economics. States also can be irrational, hesitant and indecisive; and states have shown these tendencies more than they have been rational throughout history (this is realism, not some general social law these "realists" are trying to come up with); this is why whole nations, ethnicities and long-standing empires can disappear and have done so. There are of course other exogenous covariates, most prominently environmental ones, but this doesn't rule out the effect or reality of wrong decisions. So there's no guarantee that U.S. will leave Middle-East to its own devices, and I think the assumption that it can is naive and casts aside the dynamics and realities of politicking in U.S. (casting aside realities on the ground when it comes to things other than supply lines and geographical factors is Zeihan's specialty it seems.)
imo, U.S. will support and back Israel until the costs of doing so overrule the influence of Jewish magnates in finance, politics, media and entertainment; the breaking point will come much later than it did for Apartheid South Africa due to the lobbying influence of wealthy and influential Jews, but it will come eventually as those influences are also on the downturn (but the trend is slow and the hardest thing for people to notice are the slow trends which they are living through). I think the costs overruling the Jewish influence in the west is inevitable also partially because of the dynamics of hatred spiral and catch-22 that the relation between Israelis and Muslims in middle-east has devolved into. Zeihan's problem is assuming the staticity of the current political order in middle-east. You cannot assume staticity in politics ever. And when the status-quo changes it tries to allign with public opinion more than the previous order, because that's why it's changing and it also seeks and needs legitimacy more.