No, that's not the real ending, that's what you get for beating Easy mode.
The real ending is a cutscene like the intro:
Zero Wing said:
CONGRATULATION !!
A.D.2111
ALL BASES OF CATS WERE
DESTROYED.
IT SEEMS TO BE PEACEFUL.
BUT IT IS INCORRECT.
CATS IS STILL ALIVE.
ZIG-01 MUST FIGHT
AGAINST CATS AGAIN.
AND DOWN WITH THEM
COMPLETELY! GOOD LUCK.
And I have the cancan the dancing beans use recorded and stuff if you want it.