Zero very frequently is at the stables, be it taking horses out for rides or just napping/relaxing there. Maybe they could end up meeting there at some point? I'd totally be up for sparring and such, too, handwaving being all the better, since I admittedly suck at writing that stuff out.

OH. He also knew Hange for a bit while she was in the game, with brief talk of their worlds having come up. (which was here!)