Combine the lemon zest, lemon juice, olive oil, garlic, rosemary, thyme, mustard, 2 teaspoons salt in a sturdy 1 gallon resealable plastic bag. Add the pork tenderloins and turn to coat with the marinade. Squeeze out the air and seal the bag. Marinate the pork in the refrigerator for at least 3 hours.

When you're ready to cook, build a charcoal fire or preheat grill. Brush the cooking grate with oil to prevent the pork from sticking.

Remove the tenderloins from the marinade and discard the marinade but leave the herbs that cling to the meat. Sprinkle the tenderloins generously with salt and pepper. Grill the tenderloins, turning a few times to brown all sides, for 15 to 25 minutes (depending on the heat of the grill) until the meat registers 137 degrees on the thickest part. Transfer the tenderloins to a platter and cover with aluminum foil.

Season with salt and pepper.

Allow to rest for 10 minutes. Carve in half-inch thick diagonal slices and serve warm.