we are using the web API (SOAP) as a backend in our salesforce app. Do I need to attach the ZAP/Burp or Chimera report with my submit material ? or these reports are only required for WebAppliaction . ?
Please suggest
You should consult Salesforce Security team for more formal answers. They can be reached via scheduling an office hour as documented here.
Sharing from personal experience working on ISV projects
If you are using an API other than Salesforce API itself it does need to have a BURP/ZAP scan report attached. It is not be limited to just the web application.