Wow...zig-zagging up a climb is pretty common...up steep ones, anyway. Moreover, the concept should not be that foreign, because as pointed out, it's why switchbacks exist. This is ancient practice, guys...literally.

All that said, the OP should not need to zig-zag up anything but the steepest climbs, which are pretty rare. If they're finding difficulty climbing most hills, perhaps a change in gearing, or even reviewing how to use gears, would be helpful. Thing is, an MTB is typically geared quite low, lower than most road bikes, so I'm a little confused as to why this is being done.