I don't know how good or bad the Alum salts would be compared to poly aluminum chloride. All the papers you linked to referred to using PAC, not to using just alum floc.chem geek,
How good approximately , if any, would the new formula Natural Chemistry product with Alum versus Aluminum Chloride be at removing iron and other metals, versus the old formula in percentage terms?
Would the baquacil oxidizer being a stabilized hydrogen peroxide solution, and not breaking down as quickly in sunlight, make any difference to the overall method, or results; bearing in mind the HP and AA method recommended above neutralizes the HP before sunrise with large chlorine additions?
A question in regards to Zinc Chloride, I have read that it is used in the galvanization of metals, iron being one of them. Could it be used to the protect the motor, or other metal parts present in the pool? This might be the case if Lanthanum(iii) Chloride Heptahydrate is in someway corrosive to metals. Or would it bind/galvanize, in the presence of HCL acid, with iron to make its removal easier?
The Baquacil oxidizer having stabilizers usually means metal chelating agents such as polysulfonic acid since some metals (such as iron, copper, manganese, nickel and chromium) catalyze the breakdown of hydrogen peroxide, but ironically silver improves stability. The solutions are also kept at lower pH which also helps with stability. Acetanilide may be present to reduce the breakdown of hydrogen peroxide in sunlight. The only difference this makes in the method is that it can be done during the day rather than only at night.
Zinc cannot be used in pools because chlorine oxidizes it. Galvanized steel is zinc coated and the zinc helps to protect steel from getting oxidized, but zinc itself is relatively easily oxidized by chlorine. You can put in a zinc paper clip into pool water for a day or two and you'll see what I mean. The lanthanum chloride heptahydrate is not corrosive to metals. Zinc ions in the water won't galvanize anything. They are already oxidized and won't revert to being a metal. Instead, they might form oxides that can stain if the zinc levels get high enough.