If you can recruit another unit, even Hastati, do it. When you do attack Greece and its islands, do not let up the pressure. Sometimes the unit won’t rout, even if it is simple Town Watch, until almost all of the men have been slain. Experience, especially a lot of it, is devastating. Another thing to note, the Brutii temples receive an experience bonus for troops: they won’t rout just as easily. Because you are fighting the richest of the Romans, you need your very best troops for this. When you have subdued the Scipii, you should prepare for a land invasion of Greece similar to how you attacked North Africa.
The Scipii are more important because they directly threaten your territories. If not, you will just have to hold the line against them. If you didn’t focus much on the lands east of Germany, where Dacia and Thrace is, the Brutii do not share a land border with you. The eastern factions should finish off the Scipii. Take Sicily, take Capua, and your job should be done. When you achieve this, solidify your navy, and take all the islands in the western Mediterranean. If the Scipii lose North Africa, their lands will be sundered apart. Use mercenaries, bribe enemy troops, do anything to keep your African invasion alive. Gather an army as fast as you can, with your best general in it, sail to North Africa and do to them what Hannibal did to Italy. If you have allowed them peace on their eastern front at the start of the war, they will have bigger coffers than you, and that also means defeat. If your navy is not numerically superior, you WILL lose, because the Scipii have better ships. Most likely than not you cannot destroy a naval invasion of that scale. The Scipii are the strongest naval power around, and they will launch massive navies escorting equally massive armies against you. The Scipii have most of the islands west of Italy, the whole of North Africa, and are likely to be fighting Egypt or what Eastern power has conquered those Egyptian lands.
They should also have one or two islands near Greece. It may or may not have expanded to Turkey, or even to Asia Minor. The Brutii empire is in Southern Italy as well as Greece. If you didn’t, then defeat is already certain. If you have built a strong navy, defence of your Western European provinces shouldn’t be a problem. The Julii have the upper-hand in this war. The Senate often disowns one faction more than once. In rapid succession, the other Roman families, including your own, will get disowned. The least-loved Roman family will get disowned by the Senate, triggering the Civil War. From the start, your faithful allies the Senate, Scipii, and Brutii would have expanded and made their own empires (the Senate, however, is stuck in Rome.) You weren’t allowed to break alliances or do any aggressive maneouvers on your Roman allies’ territory. The Roman Civil War is a game-initiated event. As you finish off your foes, the Julii empire is being formed. Once Spain is conquered, and your armies are out of the Pre-Marian era, you can start murdering the Britons, withdrawing your support for the Gauls, backstab the Germans… But one at a time, of course. Even the elite Spanish infantry unit, Bull Warriors, don’t stand up to Early Legionary Cohorts… If you use the Legionaries’ superior defence stats properly. They have bad unit rosters, and by now you should have had the Marian Reforms, so Roman Cavalry or Legionary Cavalry should handle those Longshields well. You should make the Gauls your protectorate by this point in time. The Britons often end up fighting the Germans, so leave the Gauls with a province or two to protect yourself from the Britons. Get German support, exchange trade rights, maybe even an alliance, depending on the Senate’s policy towards them. Attacking the Germans first leaves you unprepared for their powerful charges, and allows the Gauls and Thracians and Dacians to flank you.