I don’t mean to disagree for the sake of disagreement, but unless I am terribly wrong (and I am quoted on the Speedplay manufacturers own website for saying this in a review published originally on my store website)- the Zero and X series pedals have the same degree of rotational movement. The zero has the capability to restrict the range of rotation all the way down to zero degrees from the original amount introduced on the “X” series.
Also, I would arguee the Zero are easier to disengage since the disengagement starts at the end of the rotational movement you dial in to the Zeros.
In other words: If you set your Zeros to 5 degrees of rotational movement, release begins to occur at the outer limit of that range of motion, i.e. 2.5 degrees from the center of the rotational range of movement if it is adjusted to be symetrical (half of the total 5 degrees).
On “X” series pedals, if you need only five degrees of rotational movement for the rider (and most riders do use about that little in normal race environments) you must travel their full **28 degrees **of rotational range of motion to disengage. That is a lot of rotational movement to disengage.
Somewhat cryptically, the Speedplay website reports the release angle of the Zero series as “+/- 0-15° adjustable”. I don’t really understand how to interpret that. I guess any interpretation means that release occurs at 28 degrees for “X” series pedals, but could potentially occur at a range of 0 to 15 degrees (or 2X15 degrees: 30 degrees, if the rotational range of motion Speedplay refers to when they say “15 degrees” only represents rotation from the center orientation or range of travel trhough the total rotational range- my interpretation) for Zero pedals.
For comparison sake most other clipless pedals such as Look, Time (older, pre-“Impact” styles) and Shimano SPD/SL road pedals tend to release around 14 degrees rotation. That is half the rotation needed to escape “X” series pedals.
A lot of our “X” series customers report they have “Turn their foot too far” to escape their pedals. They don’t have that problem with Zeros since an appropriate release point can be dialed in to their preference.
In simple terms: It is easier to get out of Zeros than “X”'s.
Also, there is some difficulty in the first 3-8 engagements of brand new, out of the box Zero pedals from our experience. This appears to be the result of the molding/machining of the polymer body of the Zero pedal interfacing with the new, foul-resistant flat spring on Zeros. Once you clip in 3-8 times, that does go away completely.