# their horses' hooves are like flint

Possible meanings are 1) Isaiah compares their hooves to flint so to describe the frightening image of their feet causing sparks as they run or 2) Isaiah compares their hooves to flint to emphasize how strong their hooves are which enables the horse to do whatever their master want them to do. 

# their chariot wheels like storms

"the wheels of the chariots will spin like a windstorm" 

# chariot wheels

These wheels often had sharp blades attached to them that would cut to pieces anyone the chariot passed close to.