The last 2 month I spend improving my Petrus times. (but I believe all this applies to ZZ as well)
1. I tried EJF2L (I an Im case of MGLS) to simplify Step 2 - (it's appliable in Step 4 , too) --- MY PROBLEM IS - Most time in Step 2 I need for finding the 3 pieces, not in solving them.
2. COLL + "Last 5 Edges" (<- From L2L4) {{to simplify Step 2 - (it's appliable in Step 4 , too) }} --- That really means only tracking 2 pieces instead of 3. (instead of the F2L EDGE you place any U Layer Edge) --- MY PROBLEM IS if I place th U-Layer Edge missoriented I have to use extra mind power for Step 3 (Edge Orientation)
3. Partial COLL - When I first read on this forum COLL recognition would be faster than PLL recognition I didn't believe that, but meanwhile I recognize many of my favorite fast COLLs the moment I see the OCLL case --- This definitivley makes me faster. (and I think it's a quite common strategy )
4. Phase recognition - that means in sometimes at the End of F2L (step 4) I just see what the edge case is (If its just 1 move I still aktivly phase). Now I just pick a suitable COLL (e.g. Sune or Antisune or Niklas), that way I'm able to narrow down the range of possible PLLs (often down to just 2)
This sounds compex, but even selecting and doing an N-perm is faster for me than full PLL recognition + execution for my favorite PLL.
- My personal feeling is that this way of solving is the fastest LastLayer stategy I can do currently.
EXPERIMENTALs
STEP2 MGLS: The idea is simple - plan ahead full step1+2 during inspection

... since this is pretty much impossible skip one Corner completely to make it easier - this is very similar to EJF2L - This would almost be a full step skip every solve


- but it's above my processing power
My next MGLS idea was to merge Step 2 and Step 3 together (and again not solving the Step 2 corner at all ) - that means orienting all edges wihle placing both Step 2 edges, --- It feels a little bit like EOLINE to me (with the bonus that at least 4 edges are already oriented), maybe it would be a good simplyfication to only orient U and D edges during this merging step ???
I would be interessted if anyone tried things like this?
P.S. My Roux times improved even without traininig, so I didn't fullfill my signature goal