Pat the chicken breast dry and season both sides with sea salt, black pepper, and fresh lemon zest.
Preheat a grill or grill pan over medium-high heat and lightly coat with a touch of oil if needed.
Grill the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F and the outside is nicely charred.
While the chicken rests, whisk together the extra virgin olive oil, balsamic vinegar, lemon juice, and Dijon mustard in a small bowl to create the vinaigrette.
Slice the strawberries and roughly chop the walnuts.
In a large serving bowl, combine the mixed greens, blueberries, sliced strawberries, and walnuts.
Slice the rested chicken into thin strips and place them on top of the salad greens.
Drizzle the zesty vinaigrette over the salad and serve immediately.