In a 3- to 4-quart pan, bring about 2 quarts water to a boil over high heat.
Meanwhile, melt butter in a wide frying pan over medium-high heat.
Add zucchini, bell pepper, garlic, and thyme; cook, stirring often, for 3 minutes.
Add pine nuts; continue to cook, stir-ring, until zucchini and pine nuts begin to brown (about 4 more minutes).
Remove from heat; keep warm.
Add tortellini to boiling water and cook, uncovered, until just tender to bite (about 4 minutes).
Drain well, add to zucchini mixture, and mix lightly; season to taste with salt and pepper.