I cut them in 3/8 of an inch cubes, boil them for 90 sec in salted, chill them in ice water, mix them with cherry tomatoes, chopped parsley, green onions, a little olive oil and some balsamic vinegar. Great summer salad.
Blanching just shortens it's lifespan in the tank really. I feed zucchini to my plecs and if I blanch it, it'll be gone by the next day nothing left but the rind. If I don't blanch it it'll last an extra day or so. Blanching just makes it softer and easier to tear apart. There is no harm in just feeding them raw if you wanted.
blanching is not simply boiling. blanching is when you boil it quickly and then submerge it in ice cold water to stop the cooking... this kills any potential parasites, softens it a bit, and then rapidly cools it so it won't go any softer.
I would also remove the seeds and pulp, as they can cause a mess, and the fish can't really eat the seeds.
I think blanching is the way to go, and wouldn't leave it in tank more than 24 hours.
I also like the freezing method. I slice cucs, squash, mango and more and freeze it in a large freezer bag. I am even growing organic squash for my pleco in my garden, with the plans to slice and freeze. He will actually "beg" if I don't have something in there for him, I try to put something in there every other day and if I'm running late he'll pace back and forth where the clip usually is, LOL.