Is zig zag flashing vision symptom of stroke?

No. These symptoms most probably in your age is ophthalmic migraine with or without ensuing headache. See your neurologist or eye-md for work up.
No - migraine. Can have these symptoms, even without a headache. Please see your doctor and consider a referral to a neurologist. A full vision evaluation may also be of benefit.
Migraine. That kind of vision is often associated with migraine. There's a type called acephalgic migraine which usually has the zig zag lasting about 20min and going away.
Ocular migraines! Ocular migraines are a form of migraines that take place in the occipital cortex (part of the brain that interprets/controls vision). They lack the severe headache as common migraines. The symptoms are usually all or mostly visual and are typically described as flashing of light or ziz-zag lights in the vision. They usually last less than 30 minutes and affect the vision out of both eyes.