After you return to your own time, you go back to 600 A.D. in your quest to save the future.
New Game +
Exit Truce Canyon
Go west, and make your way through the area to leave Truce Canyon and reach the overworld.
Cross Zenan Bridge
Go west, then south, to reach Zenan Bridge. Talk to the guy in gold armor. Then go east, then north to Guardia castle. Go east, and down the stairs, and talk to the chef. Then go upstairs and approach the exit of the castle, and there will be a cutscene. Then go south to leave the castle.
If Robo and Lucca have not yet learned the Dual Tech Fire Punch, put them in your party and fight monsters in Guardia Forest until they learn it.
Go back to Zenan Bridge and talk to the guy in gold armor again. Give him the Jerky. When the attack begins, talk to him and say you'll help him, to get a Gold Helm.
Switch Lucca and Marle into your party. Go west. First, defeat the Deceased with magic (Lucca and Marle will kill them in one shot, but Crono won't, so leave him to move last), then use a physical attack on Ozzie. Go left to fight more Deceased, then hit Ozzie with a physical attack again.
After this second batch of Deceased, switch your party to include Robo and Lucca.
First kill the top half with physical attacks, then use a Mid Ether on whoever just lost their MP (unless it was Crono), then use Fire Punch on the bottom half, with Crono focusing on healing, until it is defeated. Zombor has a powerful drain attack that inflicts about 200 HP of damage, which is probably more HP than any of your party members have. Have Crono focus on using Revives as needed if anyone dies from this, while Lucca and Robo continue using Fire Punch.
Go west to exit the area.
The town of Dorino is nearby. Go to the northern part of town and enter the Residence. Check on the sparkle and talk to the old man, then check on the sparkle again to get a Magic Tab.
Go outside and go south. Enter Fiona's Villa and open the chests (Mid Ethers).
Go outside and go south, and you will see the town of Porre. Before you go to town, go northwest and enter the Cursed Woods. Go north and open the two chests (lower: Mid Tonic; upper: Shelter).
Keep going north in the woods. If a Nu (round blue creature) appears, try to get into a fight while it is on screen, and it will join the fight. It gives a lot of experience points. Its only attack is to take you down to 1 HP, it can't kill you. The other monsters can, though, so try to get rid of the other monsters first, and if any are still there, heal up if you're at 1 HP.
Then go north, and climb down the bush in the middle.
Go south and explore the room, and Frog will appear. Talk to him if you wish. Then open the chest on the right (MagicScarf) and leave.
Go south to exit the woods, then go southeast to Porre. Go into the Market and take the Power Tab in the corner.
When you are ready, go north to the town of Dorino, then go east and enter the Denadoro Mountains.