First, that is good, that you are back on the rails.
There is this page for simplified general information on credit checks in CH (it exists in English as well, just pick EN from the languages list).
https://en.comparis.ch/privatkredit/bonitaetspruefung
To learn about the period, while your misfortunes will affect your credit checks with ZEK, you can address this document:
https://www.zek.ch/getattachment/ec9ffde2-9fc0-440f-b38d-34bdbde0fc5a/Liste-Aufbewahrungsfristen.aspx
from this page:
https://www.zek.ch/de-ch/kredit-leas...ahrungsfristen
What can improve results of your ZEK checks is a well maintained loan from any ZEK partner, willing to give you one. Depending on your code you may or may not have a chance to get a loan. Following are some information about this:
https://www.credix.ch/kredit-blog/29...K-was-tun.html
Hope, that it helps.