Combine first 4 ingredients; set aside.
Preheat grill or grill pan over medium-high heat.
Brush olive oil evenly over both sides of zucchini slices. Place half of zucchini on grill rack or grill pan; grill 2 minutes on each side or until lightly browned. Remove from grill or grill pan. Repeat procedure with remaining zucchini.
Layer bottom half of focaccia with cheese, zucchini, mayonnaise mixture, Grilled Lemon-Herb Chicken, bell peppers, and top half of focaccia. Cut into four wedges. Wrap in foil or parchment paper; chill.