Okay... so you have two subjects in a sentence. How do you diagram it? Here are some simple steps.
1. Look for the subjects.
2. Draw this shape as the beginning of your diagram.
____ / I
3. Write the first subject on the top line and the second subject on the bottom line.
4. For the conjunction between the two subjects, draw a dotted line vertically as shown above. Write the conjunction
on the line.