It would take forever for me to explain everything. ✬

I can't explain it either. ✬

It would take me too much time to explain to you why it's not going to work. ✬

It's impossible for me to explain it to you. ✬

Would you be kind enough to explain it to me? ✬

I'll explain how to take this medicine. ✬

I'll explain the matter to you later on. ✬

Would you explain it in more detail? ✬

Would you explain it again? ✬

I'm afraid I didn't explain it too well. ✬