I don't know about Speedplay Zero, but I rode Speedplay Frogs for years on my Dean, and still ride them on touring bikes that I ride overseas (one pair of shoes has to do it all, walk, hike, and bike). I switched to SPD-SLs because after 40+ years of riding, I got hotspots for the first time, and it wasn't pleasant. I changed to Lake Wide shoes and the -SLs, and no more hotspots. I think the hot spots arose after my former shoes shrunk after being soaked in a downpour, combined with the narrow contact area of the Frogs. So .... my formula to avoid hotspots is more in having a shoe with adequate "toe box", and secondarily, a shoe with wide contact area and stiff sole.
Yes, the -SLs are much easier to engage the pedal than standard SPDs. I use the float cleat, not the bulbous no-float cleat. I'm a rec rider, so I want all the float I can get ... spoiled by the Speedplays.