If you combine (remix) two or more existing Creative Commons-licensed works to create a new work, then you must ensure that their original licences are compatible:

CC License Compatibility Chart by Creative Commons, licensed under the Creative Commons Attribution 4.0 International licence (CC BY 4.0)

Note that ShareAlike-licensed works can only be combined with works subject to the same or a less restrictive licence.*

If one or more of the works are NoDerivatives-licensed then they cannot be combined (or rather, you cannot publicly distribute your new, combined work). 

If you want to share an adapted work publicly under a Creative Commons Licence, then you must ensure that it is compatible with the original work(s) you have derived it from:

Adapter's license chart by Creative Commons, licensed under the Creative Commons Attribution 4.0 International licence (CC BY 4.0)

In this chart, compatible licences are shown in green. Yellow indicates that the licences are technically compatible, but care should be taken to identify the multiple copyrights and licensing terms present in the original works for the benefit of downstream users.

Adaptations of NonCommercial-licensed works can only be shared under similar NC licences. The same goes for ShareAlike-licensed works.*

Adaptations of NoDerivatives-licensed works cannot be shared publicly.