The next pair of letters in the series AZ, CX, FU, ..... is

The series consists of pairs where the first letter moves forward in the alphabet and the second letter moves backward. For the first letters: A to C skips 1 letter (B). C to F skips 2 letters (D, E). Following this pattern, the next jump should skip 3 letters (G, H, I). Adding 3 skips to F gives us J. For the second letters: Z to X skips 1 letter backward (Y). X to U skips 2 letters backward (W, V). Following this pattern, the next jump should skip 3 letters backward (T, S, R). Subtracting 3 skips from U gives us Q. Alternatively, each pair consists of opposite letters where the sum of their numerical positions is 27 (A1 plus Z26, C3 plus X24, F6 plus U21). The first letters follow the sequence 1, 3, 6, which increases by 2, then 3. The next number is 10, which corresponds to J. Its opposite letter is Q. Therefore, the next pair is JQ.