If used at all, the indirect object construction is always
to X when the verb is
explain.
However, it should be noted that the indirect object of explain is almost never explicitly stated.
The indirect object is obvious from context 99.9% of the time.
Thank you for explaining the differences. [
No to me, to us, to him, ...]
The teacher explained how the machine worked. [
No to me, to us, to him, ...]
We need to explain the rules better the next time we meet with them. [
No to me, to us, to him, ...]
CJ