You don't need a Lead Sled unless you're dealing with nasty recoil. A couple small homemade sand bags would be entirely sufficient for "normal" guns. A thicker one for the front and a thinner one for the rear.
Or, a good steady bipod and your fist under the butt stock.
With sandbags, you'd have to be a stoned chimpanzee to shoot 3" groups at 50 yards with a scoped, capable gun.
And the zero thing, that doesn't apply to scopes. A zeroed scope is zeroed unless the shooter isn't doing it right. Any two shooters who use the scope correctly will hit the same spot. Not so with irons.