How would marketo work with hubspot if we were to use hubspot as a CMS and marketo as our automation tool?
Depends. Tell us more.
Probably API if you wanted them to speak to each other.
Can you add some JS in the pages for the munchkin ? Can you add some JS on places where you want to embed a form?
If the answer to questions is Yes, then no difference compared to any other CMS
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