From the main menu choose Score Challenge, then choose Gamarys Prime 3. Turn all multipliers up to x2 then choose Play Level.
Built a power generator on the left and an Icarus tower in each of the remaining spaces. When you have enough energy upgrade the middle Icarus tower and then the other two in any order. When you can activate your killstreak focus on the skorpions as your Icarus towers should be more than capable of handling the flying enemies at this stage. When your killstreak is finished switch the top left power generator for a groundquake and upgrade it when you can. Now just keep boosting your groundquake (and your Icarus towers if you feel that you need to), and you will be finished soon!