Let's go with the idea that Queen Rutela was married to the OoT King Zora.
A way to make the entire thing fit was that she was NOT the mother of Ruto. It could be something like a traditionalistic monarchy where King Zora had more than one wife. Or, when Ruto's mom passed away, he remarried or something... hahaha
If this was the case, then Queen Rutela could indeed be married to the original OoT King Zora and not be Ruto's mom. Besides, it was implied that Ruto's mom had passed away. Everything fits with this (besides the fact we don't know how long Zoras are able to live... someone said 400 years or something.)
I personally do not think it's the same King Zora, but this was just a train of thought I had so everything would fit together.