There are multiple solutions to the "Zeppelin problem", as you call it, to the point that it's not much of a problem. If you had a powerful enough pump to crea

There are multiple solutions to the "Zeppelin problem", as you call it, to the point that it's not much of a problem. If you had a powerful enough pump to create a reasonable vacuum it's far more powerful than the pump you need to compress helium if you need to lose buoyancy.