My Ridiculous Asym is the benchmark ball in my bag currently and is one of my favorite orbs in the past few years. Mine is drilled 50 x 5" x 40. The ball gets down the lane well and has a pronounced move at the break point. It is usable for me over a wide range of conditions: Medium-Dry to Medium-Wet volumes, and medium-short to medium-long patterns. The surface is 500/4000 out of the box. I use a 2000-grit Abralon or Siaair pad (new to moderately used) prior to rolling on a 25 ml, 41' pattern, then roll a couple of times later in the week on a 19 ml, 38' pattern using the same surface with some lane shine with good results across this wide range of conditions. My PSO, a lefty, let me know how much he liked his Ridiculous Asym when I was looking into buying one. He was oh so right about this ball. The performance versus price for this ball is, well, Ridiculous, especially with the low sale prices currently available.
The Zeno uses the Reax 2 core. The Reax 2 came out of the box 500/compound while the Zeno is 500/1500 out of the box. I drilled my Zeno 65 x 4 7/8" x 65 with a P2 hole. It reads early and reacts in a controlled manner on the back end. The Zeno is more useful for me with a 500/compound surface as it gets down the lane better and reads the end of the pattern better as well. The controlled layout I put in the ball which already has a controlled backend reaction is, perhaps, a little too controlled for good carry. In hindsight, I should have used a similar layout as my Ridiculous Asym (as well as my Guru Limited), 50 x 5 x 40 and allowed the controlled core in Zeno along with a P3 hole to provide the difference in reaction. Yes, these two balls do work well in the bag without any overlap. The Zeno is a step down from the Cash and Guru/Guru Master so it doesn't belong at the top of one's bag but is a good control ball for challenge patterns and other patterns featuring dry back ends. The Cash and Guru/Guru Master are better suited for long patterns and/or wet back ends.
Brandon Riley and CoorZero have good takes on the Ridiculous Asym/Zeno combination. I like BowlingforSoup's input as well. I have a Cash that utilizes the 90 x 2 1/2" x 50 low flare layout and it, too, is smooth on the back end. The layout, in this case, dominates the core/coverstock's natural tendency to move smartly off of the end or side of the pattern.
I also have a Ridiculous Pearl that I don't like as well as the Asym. The Pearl reacts too hard off of the end or side of the pattern and tends to squirt when it sees conditioner down lane. It is not as forgiving nor confidence inspiring as the Ridiculous Asym for my game and conditions I encounter. Just goes to show how important the core to coverstock match is.
Hope this helps LuckyLefty!