Hi @flongchamp - in a perfect world, those two sessions on the same day would best be done back-to-back…but if splitting them up works better for your personal schedule, then there’s very little difference in splitting them apart.
In the case of a high intensity session and an endurance session on the same day, we sometimes would recommend splitting the sessions to allow for a little more quality in the second session - unless your primary goal is a longer event where there’s value in performing the added lower intensity/volume of riding while more fatigued from the first effort.
So, in summary, the true difference in potential response to two back-to-back endurance sessions versus a single session is likely small enough to truly no matter much…in which case, do the method that best fits your personal life situation!