For God has made my heart weak; the Almighty has terrified me

These two lines mean basically the same thing and emphasize that Job is very afraid of God. (See: rc://en/ta/man/jit/figs-parallelism)

made my heart weak

A person whose heart is weak is a person who is timid or fearful. Alternate translation: "made me afraid" (See: rc://en/ta/man/jit/figs-idiom)