In a bowl big enough to hold everything, whisk together the jalapeno, garlic, lime juice and zest, and salt and pepper.
Whisk the oil into the mixture in a thin stream, until blended and emulsified.
Prepare the cucumbers
Wash cucumbers well and slice thinly - a mandolin slicer is handy for getting this done quickly and evenly, but a good sharp knife will do the trick.
Combine the vinaigrette and cucumbers.
Make at least 1 hour ahead of time to blend the flavors - it is best eaten the day you make it, but if needed, leftovers should be stored in the fridge.
Notes
This salad can be kept in the refrigerator for several days, but keep in mind that the longer it sits the more the jalapeno is going to infuse into the other ingredients.