Apple's "engineers" didn't learn much about deflection and material stiffness when they went to "college", so this optical drive is particularly difficult to remove because the bracket flexes too much. The next few steps require some patience and a good amount of force.

Insert the flat end of a spudger into the gap between the optical drive and its bracket until it contacts the chassis.

Grab the spudger as close to the surface of the optical drive as you can, then depress the release tab with your thumb while pulling toward yourself.

The wedge shape of the spudger may cause it to slip out of the gap toward yourself. Be sure to press the spudger in toward the rear case while squeezing the release tab.