What is this plant
It certainly looks like zucchini but you do realize you planted a bush variety. It will not get the long vines. Also, zucchini really doesn't do well until both the soil and air are warm. Information I have found said the soil should be 60 degrees before planting. I don't believe the soil was that warm in mid May but your seeds did sprout. However, they probably got a slow start. They take approximately 60 days to start to flower so they should be starting to flower soon. Another Master Gardener has pointed out that he thinks he sees a flower bud in the middle of your leaves. If that is so, it may be a sunflower. The bloom will be the final answer. If it is a sunflower, your seeds did not sprout. Maybe the soil was too cold.