Fall of Constantinople 675AD

this timeline is based on the supossition, why if the Umayyads didn't focused on the northern african regions if not in the rich Byzantine Empire core, Greece and Anatolia, taking this as the base, the Umayyads through a great force to an empire that has faced defeat 40 years before, and despite The Roman empire remnants fight hard it ends up with an utter defeat taking anatolia and Most of Greece, Only Remaining Independent Creete, Cyprus and Byzantine Italy and North africa ( as the war would i've been in the Core) my question is, is this plausible in any possible way, for the Umayyad Caliphate, if its Implausible i can change the Basis ofthe timeline