No, and it is worth being plain about it. El Jem to Matmata is about 207 km in a straight line, Matmata to Douz another 68 km, and El Jem itself is roughly 174 km south of Tunis. Attempted in a day from the coast that is more than 700 km of driving for perhaps two hours out of the car. The three fit naturally into a two- or three-day circuit, which is how they are normally combined.
About 207 km as the crow flies, and appreciably more by road. They are in different parts of the country: El Jem is on the Sahel plain, Matmata is in the southern hills above the desert.
Two days, staying overnight in the south. Three days is more comfortable and adds the Chott el Jerid salt crossing and the oases at Tozeur.
It is the third-largest Roman amphitheatre standing, and you can walk the arena floor and the tunnels beneath it. It sits directly on the road south, so it costs almost no extra driving on a Sahara circuit.
Distances are straight-line, measured between the coordinates on our map of the sites; road distances are longer. Prices are per vehicle and come from the same database the 28 tours and 1,392 transfer fares are quoted from.