Hi,
I am by no means an expert on the subject but the way I understand and use the delay works very well indeed.
I have never used the Zoom system so am not familiar with it but reading user reviews there is a full delay effect built into the unit with the edit facility needed to alter the settings, so you don't really need a seperate pedal. I use the Digitech RP6, a basic unit but it'll do for now. Your unit should have very similar basic settings.
Firstly, there is the TYPE of delay - mono, stereo, multi-tap etc. The tap delay is simply set by 'tapping' the relevent button or pedal to set the tempo of the delay you require. I've read that Edge uses the mono delay, so that's what I use.
Second, is the LEVEL of the delay. This figure sets the strength or fullness of the delayed signal. The higher the setting, the more strength the 'echo' has. On the RP6 this ranges from 0 to 100, so a setting of 100 will produce a delay as strong as the original signal, 50, half as strong etc.
Thirdly, is the TIME. This is where 'ms' or milliseconds comes in and is the time between the note played and the subsequent echoes. The lower the figure, the faster the resultant delay. My unit ranges from 0 to 800ms. I think that 500ms is half a second.
If you listen to some of U2's live tracks you can hear Edge do a signal check just before the song starts, especially before Pride on the Elevation tour. This is where he hits the muted strings once and the delay is clearly audible. There are a number of 'ms' timings that can be used for any given tempo but to play the song properly the exact right one has to be chosen and your playing timing has to be impeccable.
Lastly, is the FEEDBACK setting. This is the amount of delay produced from the original signal. The higher the figure, the longer the delay will 'echo' for. The RP6 ranges from 0 to 99 and a setting of 99 will give an infinite delay. For instance, set the LEVEL to 100 and the FEEDBACK to 99 and the delay will be as strong and loud as the note you picked and will 'echo' constantly.. Conversely, if I set the LEVEL to 50 and the FEEDBACK to 0, the note will 'echo' half the strength of the original and repeat onlt once. At higher feedback settings, each subsequent delay will tail off or get quieter towards the last 'echo'.
For an example, my settings for Streets are:
TYPE - Mono
LEVEL - 95 as I require a strong delay.
TIME - 370ms Elevation tour version.
FEEDBACK - 35 I only want about 4 discernible echoes
otherwise the notes become mixed and
muddy.
I Still Haven't Found What I'm Looking For:
TYPE - Mono
LEVEL - 95 this also requires a strong 'echo' for the
picked notes to sound effectively.
TIME - 440ms
FEEDBACK - 35 again, not too many 'echoes' or it'll
sound muddled.
As I said I'm no expert but I hope this helps you a little.
Don't forget the points regarding a low level of distortion and especially about the type of pick you use.
Happy playing,
PEACE!
All the best, Daz.