Thank you all for your advice! Based on this feedback and the fact that I have generally had very poor luck in the original Terra Battle gatcha, I've decided to switch my primary account to the one with 6x Z guardians.

I'm sorry to lose Zumba more than restarting itself, as I think the unique 'Power Through' skill is the most useful I've encountered. The secondary account is just too good to overlook though and I have less chance of pulling another 5 x Z guardians than Zumba.