Combine the lemon zest, lemon juice, 1/2 cup olive oil, garlic, rosemary, thyme, mustard, and 2 teaspoons salt in a medium bowl or a 16-ounce glass measuring cup.  Trim the pork tenderloins and place them in a sturdy 1-gallon resealable plastic bag.  Place the bag in a large baking dish or pan.  Pour the marinade over the tenderloins and turn to coat all surfaces.  Squeeze out the air and seal the bag. Marinate the pork in the refrigerator for at least 3 hours but preferably overnight.

When ready to cook, build a charcoal fire or preheat the gas grill.

Brush the cooking grate with oil to prevent the pork from sticking.  Remove the tenderloins from the bag and place them on the prepared grill leaving the herbs that cling to the meat.  Discard the marinade or heat to boiling to serve with meat (see note).  Sprinkle the tenderloins with salt and pepper.

Grill tenderloins, turning a few times to brown all sides, for 15 to 25 minutes (depending on the heat of the grill and the size of the tenderloins) until the meat registers 137° at the thickest part.  Transfer the meat to a platter and cover tightly with aluminum foil.  Allow to rest for 10 minutes before slicing.

Carve in diagonal slices of 1/2 inch to 1 inch in thickness, depending on your preference.  The thickest part of the tenderloin will be pink (which is fine) and the thinner part will be well-done.

Serve warm or at room temperature with the juices that collect in the plate.  Garnish with additional fresh herbs, such as sprigs of rosemary and/or thyme.  Optional grilled lemon can be added.

NOTE:  Marinade can be used to serve with the grilled meat but MUST be cooked thoroughly to kill bacteria.  Bring to a boil, then lower heat and simmer for a full 10-15 minutes.