Much of this depends on the terrain and vegetation. I've hunted the Zim lowveldt four times and will return next August. My .375 H&H wears a Leupold VX6 2-12x with their Firedot reticle. That model is discontinued and replaced by their VX6HD 2-12. These have excellent eye relief (helpful on a .375) and the lower magnification range works well for the thick stuff, but you can crank it up for longer shots. The Firedot feature is very handy for dark colored game in thick bush, like when hunting Cape buffalo. The Firedot LR Duplex reticles has a couple "dots" below the crosshairs and those are useful for setting up longer shots at 250-400 meters.
Of the three scopes you mention, I'd go with the VX5-HD 2-10 for those reasons, and would get 171389 with the Firedot. It appears that the LR reticle is no longer offered, but the VX6 and the VX5HD have uncapped elevation dials and one could simply dial for longer shots. I simply replace the lithium coin battery before each hunt. I run a VX6 1-6 on my .458 Lott, also with the Firedot reticle. Both rifles have iron sights and the scope is on a QD mount, but I've never found a need to dismount the scope when hunting. Leupold changes models frequently and you can often find discontinued models greatly discounted (at least in the USA). Good luck!