Rachel, frozen Tomatoes, Zucchini, &
ALL "Produce" are safe in the freezer for an indefinite period of time. Tomatoes especially, are too high in acid to support the Clostridium botulinum spores that produce the toxin which causes Botulism poisoning in the first place (unless they are overripe, bruised or moldy), but it is virtually impossible for enzyme action to take place in freezing temperatures.
Depending on how they were packaged for freezing & how cold the freezer is maintained over time, they
might get freezer-burned, which will affect the flavor & texture, but they're perfectly safe, providing that they don't remain at room temperature for a long time before being eaten or used in cooking.
Here is a link to recommended
Refrigerator/Freezer Approximate Storage Times .
