So I have been doing variations of this with my own plans. To make a long story short I’ve come to the conclusion that if I’m going to be combining plans then I’m going to have to be OK with slow progression, or at least not progressing as fast in one area as I would like. I think the UA authors have said this many times but I’m stubborn and had to learn the hard way.
I say that because trying to do both plans as written at the same time (a total of 4 strength workouts a week), with the aerobic volume and work changes and family, quickly led to me being way too exhausted, and I felt like I was just getting more tired and not fitter.
So less is more. What I do is cut each plans volume in half and combine it together. It could work for you because one plan is more upper body and one is lower body (I would guess).
A simple example is where it says to do 2 workouts a week I just do 1 from each plan so the total is 2 and I’m not over training, then on the high volume weeks (weeks 3 and 7) I may do a total of 3 workouts (2 from 1 plan and 1 from another) followed by a week of 50% volume and maybe 1 strength workout.
Or Maybe start the Ice and Mixed Plan and only do Maintenance workouts for your Mountaineering Plan. Then after the first 8 weeks take a week off and start it again with the Mountaineering Plan.
Make sense? If anybody thinks I’m off base here please throw a wrench.