I don't know based on the rulebook. The provided context does not specify the order in which simultaneous or overlapping Power effects (such as removal and Damage) are resolved when they target the same land in the same phase. It also does not explicitly state whether Damage can be dealt to Invaders that have already been removed by another effect in the same phase.

What is clear from the context:

• Removal: "Some effects remove Invaders, representing them fleeing in terror. Return the specified pieces to the supply." (page 18)
• Damage: "Whenever a Power or other effect says 'Damage', it always means 'Damage to Invaders' unless explicitly specified otherwise. When dealing Damage, it is done to any Invaders in the target land, divided among them however you choose." (page 18)
• Order of Effects: The rulebook does not provide a general rule for resolving multiple effects targeting the same land in the same phase.

To answer this question definitively, the rulebook would need to specify:

• Whether players choose the order of resolving simultaneous effects, or if there is a default order (e.g., all Damage before all Removal, or vice versa).
• Whether Invaders removed by one effect are still valid targets for Damage from another effect in the same phase.

Source: page 18, and general absence of a rule for effect order in the provided context.

Source: Core Rulebook (pp. 10, 15, 18, 21, 9)