Santa brought me Speedplay Zero pedals for my bike. Actually, a set for each bike.
First order of business was to put a set on the bike that’s on the trainer. This gives me the chance to get used to them before using them on the road.
The hardest part is always getting the old pedals off but I persevered. Once on, it was try them out.
My first observation was that my saddle was too high. Going from Look style pedals to Speedplays resulted in lowering my saddle roughly a quarter inch.
The release action seemed as easy as the Look pedals but the clip in part seems a bit more challenging. I remember my friend saying this same thing. Of course the action of clipping in is much different than the toe-heel entry action with Looks.
I like the fact that I can dial these in to have no float. I know there is a lot of talk about the positive aspects of float in pedals but there is also buzz about the lack of float. These pedals allow me to decided how much float to have in my pedals.
I’m still working on fine tuning my entry technique and would love to hear if anyone has any hints or tips. Do you have float in yours or none at all?
Maine Velophile 
I have zeros on my road bikes and have some float which, perhaps eliminated a knee problem. I have SPDs on my ‘cross bike and, voila, my knee problem flared up again. Coincidence? Maybe.
The entry thing solves itself with repetition, but a little cue that helped me is to think about a little flick of pressure from the ball of the foot. Snap and go!
Like Julie said , a little “heel down” might help. You want to have your foot parallel to the pedal for entry.
Another technique is to rotate your foot like you are “squishing a bug”. Hope this helps. Enjoy!