Has anyone actually prepared Zn(HCO3)2 absent the presence of pressurized aqueous CO2?
We have to distinguish between the bicarbonate in solution and the bicarbonate as a solid.  While many metal cations are compatible with bicarbonate anions in dilute aqueous solution, only in a few cases can a solid bicarbonate be expected as a precipitate.  In most cases, such as with lithium or with hard-water forming metals such as calcium and magnesium, the carbonate is formed instead.  The only solid metal bicarbonates I know of are those of the heavier alkali metals than lithium.