I have recently planted 4 Sicilian Zucchini which were purchased from a garden center. As soon as they went in the ground some discoloration of the bottom leaves started to occur, as well as some little holes. Not sure it is from bugs, poor soil, too much or too little water. This is the second batch I've planted. This first batch died right away. I put it off to a cold, rainy week we had. I pulled the dead ones and replaced the soil. They are flowering and growing well. Hopefully somebody may recognize the symptoms on the attached photos Thanks
It looks to me that your zucchini is planted too deep. The leaves should not be joining the stem underground. It may be causing the leaves to rot. I would remove some soil from around the stem.