Here's new footage of Diabolico, the episode starts off in new footage however it's hard to tell whether the cockpit stuff in the Aquabase is all new or not.
Exterior shot of the Skull Cavern is the usual Sentai stock shot of it but all interior stuff is new footage.
The footage goes back to Sentai footage once you see the dark cloud that lighting comes out of.
Once you see this shot of Olympius with civilains nearby, it's back to new footage.
Here's new footage of Olympius and Diabolico
The Red Ranger uses his Trans-Armor Cycle in the fight against Olympius however after the Cycle attacks Olympius, the Red Ranger stops it in its tracks for a bit as seen here
Here's a shot of the Rangers with their weapons
The actual growing and transformation of Olympius is Sentai footage as is the actual growing of Diabolico.
It looks like this shot of Giant Diabolico is new footage but once you see the zords then that's when it goes back to Sentai footage.
Once you see the morphed Green and Blue Rangers out of their zord then that's when it goes back to new footage however once you see the Red Ranger in a zord cockpit, that's when it goes back to Sentai footage. All Giant footage is Sentai footage however the shots of the Blue and Green Rangers being on the ground during the Giant footage is new while the Giant footage is still Sentai. The footage of Jinxer being outside of the ruins of the Skull Cavern by the Giant footage is Sentai footage.
The shot of Queen Bansheera's claw nails covering over the exterior shot of the planet Earth is actually Sentai footage.
The shot of the helmetless female Rangers being in the Lifeforce Megazord Bay is new footage but all shots of the Lifeforce Megazord in its Bay is Sentai footage.
The next shots of Jinxer along with the Giants Olympius and Diabolico are Sentai footage but once you see the Red Ranger, that's when it goes back to new footage.
Here's new footage of the damaged Megazord and the recovered Red Ranger Once you see the up-close shots of Olympius and Diabolico's faces again then that's when it goes back to Sentai footage.
After Giant Diabolico attacks the Red Ranger, you can see the Blue and Green Rangers in new footage however once you see the Red Ranger again then that's when it goes back to Sentai footage.
This shot of the Rangers is around the time when it goes back to new footage however once you see Olympius again, that's when it goes back to Sentai footage. The Lifeforce Megazord appears in Sentai footage however once you see the 3 male Rangers again then that's back to new footage but then it cuts back to Sentai footage of the Lifeforce Megazord. It then cuts back to new footage of the 3 male Rangers and then it cuts to Sentai footage of the Lifeforce Cockpit.
These cockpit shots are definitely new footage     but once you see the Lifeforce Megazord then that's back to Sentai footage once again. When the Red Ranger says "Lifeforce Level 3 - Energize!" that's new footage but when you see a full shot of the 5 Rangers in the cockpit then that's when it goes back to Sentai footage.
All other Megazord and Giant footage stuff is Sentai footage unless it was otherwise stated earlier on.
All footage of Bansheera and Jinxer in the interior of the Skull Cavern ruins is new footage.
The shot of Jinxer's flashback with him being in the same shot as the Lifeforce Megazord is new footage however that's all that I'm certain about in regards to it being definitely new footage.

Sentai info comes from GoGoV Episodes 49 and 50