According to an embodiment disclosed, a feedstock hydrocarbon may be processed by a method which may include separating the feedstock hydrocarbon into a lesser boiling point hydrocarbon fraction and a greater boiling point hydrocarbon fraction, cracking the greater boiling point hydrocarbon fraction in a high-severity fluid catalytic cracking reactor unit to form a catalytically cracked effluent, cracking the lesser boiling point hydrocarbon fraction in a steam cracker unit to form a steam cracked effluent, and separating one or both of the catalytically cracked effluent or the steam cracked effluent to form two or more petrochemical products. In one or more embodiments, the feedstock hydrocarbon may include crude oil and one of the petrochemical products may include light olefins.