Maybe if I asked the question like this you could better understand:
I understand the chart you have published to say commercial and investment banks have made campaign donations to the Cruz presidential campaign.
Name one.
A zero interest loan is a campaign contribution, what don’t you understand about that?? Is is not “principled” in any sense of the word.
If you want to go throught the logical, moral, and ethical contortions to defend that as something the self professed “most principled conservative in the race” should be doing, go right ahead.