Chicken gizzards are pretty tough, and unless prepared correctly will almost certainly turn out a little 'chewy' My advise would be to use a combination of marinading and simmering in water for before coating in the crumb and frying.
For the marinade you can choose whichever ingredients you feel comfortable with, but as an idea, use salt, pepper, perhaps a herb mix, minced garlic, chilli sauce or soy sauce etc. You can marinade before or after simmering, I believe after is better.
To simmer, place gizzards in a pan and cover with cold water make sure the water is a least 2 to 3cm above the gizzards. Add an onion and bay leaf. Bring the water to a boil then cover and simmer for 2 to 2 and half hours. Add more hot water if needed. Once done, let cool slightly, add to the marinade and refrigerate for about an hour. At this point you're ready to fry.
Coat the gizzards in whichever bread mix you choose by shaking together in a sealed plastic bag. then fry in plenty of hot oil, in small batches.