How to keep saute pan hot without it burning for searing fresh greenbeans or zucchini
I have seen various establishments par-cook their vegetables then finish them in whatever sauce is being used or quickly reheat them in a pan or on a flat top in oil or butter. 

Like part of your morning prep would be to cook off however many zucchinis (broil it? oven fry? up to you, you're making them in bulk so sauteing may not be the most efficient route) you're going to need for the evening, cool them on a half pan in a single layer, then store them in your line until the order comes through. Chuck them in the morning if they don't hold up well overnight, I'm not super sure how well zucchini holds up. Green beans should hold just fine for a day or two.

All you need to do then is get a serving out and saute until heated through. Shouldn't take too long, and it shouldn't leave an unwieldy mess in the pan as long as it's oiled appropriately.