This question is an exact duplicate of:
In general, one does not interrupt a mitzvah (with the exception of Torah study) in order to do another mitzvah. However, this answer, in its citation of the Ran, alludes to some complications of this precept in view of whether the mitzvot are rabbinical or Biblical.
It is not clear, however, whether one should interrupt the performance of a rabbinical mitzvah (or, say, a minhag) to do a Torah mitzvah. Is there a rule about this?
Related, possible duplicate, not sure: