Hi, Cris.
Thank you for reaching out!
Take a look at this article for information on using Multiple Completion Criteria:
You will see the following:
If a learner completes multiple criteria, do they all get sent to the LMS?
No. Only one option gets sent to the LMS, even if a learner completes multiple criteria. The first tracking option that the learner completes is the one that gets sent to the LMS.
In your scenario, the first option completed is the quiz, so the user doesn't get a chance to get completion based on the slides viewed.
My suggestion would be to only track based on slides viewed, as you would still be able to see the user's responses.
I hope this helps!