So my brother is reading the third book of the mistborn series and made a comment about the mental concentration of controlling the Koloss. He also said that it could be easier with mental speed.
That probably helps us to know how the Lord Ruler kept the Koloss at bay. He controlled them with zinc or brass, and then used mental speed, possibly compounding, to help with keep them under his control.
that also opens up the power of a zinc compounder a bit more. They could basically be the beast tamer class of the mistborn world. This could possibly work better for a zinc-electrum twinborn, but I dunno which one would work better.