You can definitely use both but you should be aware of the following:
- There will be a lot of overlap in offered features unless you take time and effort to manage it by carefully picking elements from each of those libraries. And even then you will face situations where you can't avoid overlap. This basically results in a bigger bundle.
- You will have to maintain theming variables for both systems to have a consistent presentation across your app. Even then, there will be situations like where your table checkboxes look different from your form checkboxes because they are from different libraries.
- You have to learn and understand both of the systems. It means sometimes it'll be harder to find what's causing a certain bug. You'll also be spending more time deciding which library to use for which component.
Overall, it's more work for you to work with two different systems and a higher chance of things looking inconsistent. That said, mixing in things like a grid system with limited theming might not be too bad.
If possible, I highly encourage you to choose one system and stick with it.