Yeah it will be context free.
1st part : Set of all strings with equal noof a's and B's is a standard CFL Language accepted by Push Down Automata.
2nd : sum of a's and B's divisible by 3 is regular language
And intersection of regular language and context free language is CONTEXT FREE.
Theorem : If L1 is a CFL and L2 is regular then L1 $\cap$ L2 is CFL.
Proof for above : https://www.cs.umd.edu/~gasarch/COURSES/452/F14/cfgreg.pdf
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