Is zero radius unachievable due to space restrictions?

Some scientist believe that zero radius is unachievable. That something would prevent it from happening... In Zeno's paradox he states that there are infinite halves of a set distance... but what if there are not...and space is made up of tiny quadrants smaller than strings.... that is to say the the matter is a black hole can only get so small and no smaller since quadrants are a certain size....is this possible?