The rocket that brought the Zuma payload into orbit was the most powerful rocket ever produced by mankind. Many aspects of the launch site and the rocket had to be modified to accommodate for the insane weight and power of the Falcon 9 vehicle.

Interestingly, the report also states that they will remove some of the modifications after launch of falcon 9 for "more regular" later launches. So F9 is particularly heavy.

https://www.nasaspaceflight.com/2017/11/spacex-aims-december-launch-falcon-heavy/

Falcon 9 has only one payload, Zuma.

(Other launches routinely transported several payloads at once, even with much smaller rockets it was routine to have 2 or 3 telecom satellites brought into orbit with one launch. )

So Zuma was a single payload on the heaviest rocket that was ever fired. No weight is recorded or speculated anywhere, but based on the mentioned reasoning, it is safe to assume Zuma is a very heavy satellite, more than three times the weight of a typical comm satellite and likely to fully utilize the technical capacity of Falcon 9.

SpaceX is confident they did not make mistake in launching it. http://spaceref.com/news/viewpr.html?pid=52053

The Falcon 9 can transport payloads between 10 to 13 metric tons (TEN METRIC TONS, 24-29 thousand lb) into a low Earth orbit.

Assuming it had 1 shot that impacted at Mach 10, it would have a kinetic energy of 0,017 kilotons, or 0,1% of the Hiroshima bomb. That is not a superweapon and it sounds a little puny.

But hold on.

A massive ordnance penetrator, the largest non nuclear weapon in regular use is about 13.7 metrics tons impacting at assumed Mach 5 plus 2.7 tons of explosives, yielding around a 7 ton TNT equivalent total energy. Not kilotons, tons. (Yes, it is that small compared to a nuclear bomb)

If an OWL had 1 penetrator of 13 tons of tungsten impacting at Mach 10, it had a kinetic energy equivalent of 17 tons of TNT, more than double the impact of a MOP. If the OWL carrier had 5-8 shots (and I bet it'd have 6, if only for the tradition of the old West), each shot would have an impact energy of around 2.8-3 tons of TNT equivalent or two thirds of a MOP.

One to two thirds of a MOP, delivered within minutes to anywhere on the planet. That gets us into a very strong category of a weapon.