Two different google tag manager accounts in same domain

Question

I have two google tag manager accounts one mine and another of third party website and I need to put these 2 in this third party website. I tried put two gtm scripts after body

Answer 1

This is because both GTM tags are using the default "dataLayer". See below:

Give one or both custom dataLayer names like so...(documentation):

After that you should see no duplicate events firing from either container.