look like the lower leaves are just dying off. Not sure why but i don't suspect a fungal problem. I'd be more concerned with the younger leaves curling up. Either way, they are pretty well advanced so you should get a decent crop.
The zuchinni may have a fungal problem. Are the fruit getting really thin at the blossom end? This can be from a potassium deficiency. It can also cause leaves to have 'burnt' margins.
Remove any suspect leaves and destroy them anyway. Zuchinni love a liquid feed.
The tomato looks like it has blossom end rot, a calcium deficiency, often brought about by inconsistent watering. They often recover as the plant gets a bit older. Try and water deeply every few days rather than a little bit every day and give a feed of liquid fertiliser occassionally. Mulch helps retain soil moisture and keeps the soil temperature cool on hot days.
Don't water your plants in the evening if possible. Leaves being wet overnight is a great way to spread fungal problems. If you must water in the evening, try just flooding the soil and not splashing soil up onto the leaves.