Hey there, sorry to say I would not expect these to pick up - they just don't look healthy overall. In the end it would be a better idea to buy a packet of zucchini seeds and start over - plants you have to coddle with supports are not usually ones that will end up doing you proud.

This is not actually one baby zucchini plant, but 5 or 6 individual seedlings that have been grown in insufficient light. Their stems are long, thin and weak from trying to stretch and find more light, and it looks like this has been the case for longer than the 2 days you've had them. If they kept growing, they might be stunted (their true leaves already look quite small) and never produce.

The good news is growing a zucchini plant from seed is easier and cheaper, and will probably result in a healthier plant, than buying an already-established plant. If you can, place your container in a spot with more direct sun and drop a few new seeds in there. The new seedlings grown in adequate light should have shorter and sturdier stems, grow faster and will not need support. :)