I am making a pasta that has tomatoes, zuchinni, cheese and meat. What type of side salad should I have with it?

There's so much happening in the main dish - maybe grilled peaches with balsamic drizzle and basil? Or bitter greens- grilled radicchio or even grilled escarole with lemon juice and salt. I like the suggestion of melon salad, too.

I think a simple butter lettuce salad with a zesty, lemony dressing would be the perfect complement to the meat and cheese, like this: https://food52.com/recipes/16940-april-bloomfield-s-lemon-caper-dressing

Lot's of good ideas here but I will add one more, a nice broccoli rabe salad. http://cooking.nytimes.com/recipes/828-broccoli-rabe-salad-with-roasted-garlic-vinaigrette

Try my panzanella https://food52.com/recipes/6058-panzanella-della-piazzale

Since there are a lot of flavors in the main dish, I would go with a simple romaine salad with a lemon/olive oil dressing... perhaps some toasted pumpkin seeds or other nut of your choice on it and shaved parm.

I like simple arugula with olive oil and balsamic.

Your planned main dish sounds rich, so I would go with something bitter/sharp or sweet and refreshing.
Also, suggest serving it as a separate course, after the main.
Bitter/sharp options:
*oranges and onions (sliced, use red onion or sweet onion, olives optional)
*greens only (arugula, watercress), like these bitter greens with sesame dressing:
http://www.seriouseats.com/recipes/2013/11/bitter-greens-salad-sesame-dressing-recipe.html
*anything in season that you like from the crucifer family (cabbage, kale, kohlrabi etc). For ex,David Chang brussels sprouts with fish sauce:
https://food52.com/blog/4857-momofuku-s-roasted-brussels-sprouts-with-fish-sauce-vinaigrette
Sweet/refreshing: melon & cucumber salads. Many recipes out there. Often watermelon is garnished with Feta, which I might leave out for this meal.