Why The Alien Rangers?

[Spidey]

Why did Zordon call on the Alien Rangers to help on Earth, knowing it would put them in danger due to their physiology being too different from Earth when Andros and Zhane (and presumably other Space Rangers) from KO-35 were perfectly able to live and fight on Earth?

[MattEmily]

Because he and Alpha only new of the Alien Rangers and he was likely aware of them having zords as well.

I don't believe he knew Andros or Zhane at that point in time yet and they had no zords for Giant battle purposes either.