I think my zucchini got too big for the seed starting containers they were in and have started to die unfortunately. I've attached pictures for reference but as can be seen they've turned yellow and are suffering. I've transplanted the healthiest ones outdoors into my raised garden bed and threw away the rest. Is there any hope for them? Anything I should do to give them the best chance they can have?
Yes, the new leaves are green, so the plant is healthy. It just need sun and soil(/fertilizers). Just soil was too small for such plants. You should have re-potted in larger pots (or directly on soil).
In future I would avoid using such seedling base for zucchini. It may be good for tomatoes (but with a re-pot) or lettuces, parsley, etc.
Just now we are near to the solstice, so.. you will have a short harvesting season.