I know they can't be zero at all; that's why I said "The lowest a Pokémon stat can be is 1. Any time a stat would be lowered to zero, it will be made 1 instead." It's a hypothetical statement, hence the "even if they could".
That being said, you seem somewhat confused on why that is - it has nothing to do with base stats, and while your math is correct for the real numbers, the games round everything down to an integer, which would hypothetically make a stat of zero possible. For example, if you had a Speed stat of 1 and then became paralyzed, the result would be rounded down to 0 (you can't have 0.25 Speed). However, every time a stat is lowered, the game checks if the result is zero, and if it is, it immediately sets the stat to 1 instead - hence "Any time a stat would be lowered to zero, it will be made 1 instead."