Question regarding an interesting Chain

[Synaku_Blade]

My friend and I were playing, and I was testing my Yubel deck. I activated Return From Different Dimension while Yubel - Terror Incarnate was on the field. Now RFDD's effect states that all monsters special summoned by it's effect is removed from play during the End Phase, however Yubel - TI states that during the End Phase I must destroy all monsters on the field.

Would Yubel's effect take priority due to the fact that is a mandatory trigger effect, or would RFDD'd effect resolve first?  

[Jevan R. H. Divinitive]

Synaku_Blade

My friend and I were playing, and I was testing my Yubel deck. I activated Return From Different Dimension while Yubel - Terror Incarnate was on the field. Now RFDD's effect states that all monsters special summoned by it's effect is removed from play during the End Phase, however Yubel - TI states that during the End Phase I must destroy all monsters on the field.

Would Yubel's effect take priority due to the fact that is a mandatory trigger effect, or would RFDD'd effect resolve first?

I asume this is on that players turn. You can decide which activates first. These effects won't form a chain by the way, one will activate and resolve before the other.