After exercise or standing up very i get flashing zig zag vision in corner of eyes. do you know why?

Orthostatic: Perhaps you became orthostatic after exercise or sudden change in position when your blood pressure suddenly dropped and you had the visual phenomenon you described. If it was brief and not repeating, i would not worry about that.

See Medical Doctor: This could be due to low blood pressure or other circulation problems. See your medical doctor.

Zig zag vision : Most people with have flashing lights or zig zag vision upon standing will have some amount of orthostatic hypotension. In other words, your blood pressure goes down when you stand up quickly. I suggest more fluids and to get up slowly. This should be discussed with your general medical doctor.

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.