Hello Mari and extra-sweet Zazu, and welcome to FDMB.
Well done for wanting to hometest. That will make it much easier to manage Zazu's diabetes.
Very few people get a successful test the first time they try it. So don't let that worry you. It's like anything new, it can sometimes take a
little practice to get the hang of it. But it will soon become routine.
As Vyktor's Mum says above, cats can easily pick up on our stress, so maybe try a few deep, calming breaths before the next test attempt (and yes, chocolate is good too....

)
Here is the link to the FDMB page of homestesting info, tips and tricks, and example videos:
Hometesting Links and Tips
The most useful tips I learned were:
1.
Most important: Make sure the ear is warm. Warm ears bleed so much more easily than cold ones.
2. Put a little pressure against the underside of the ear, opposite to where you're pricking, otherwise the lancet can push the ear away rather than prick it. Some folks use a bit of cotton wool or folded tissue, but I just use a finger tip (and have occasionally taken some blood from myself that way....)
3. Massaging immediately below the ear prick can 'milk' out more blood.
4. Two ear pricks close together can often produce enough blood for a test where one ear prick might not.
5. A teensy weensy smear of vaseline on the outer edge of the ear can help the blood to 'bead up' and stop it disappearing into the fur.
6. It's important to reward the kitty for each test (or attempted test) with a cuddle or a treat. (And in fact I crumble a few treats for my cat and then test him quickly while he's munching on those.)
Please know that this should not hurt your kitty at all. There are very few nerves in the outer edge of the ear. But it is a new experience for him, and for you.
If your kitty doesn't like having his ears touched then you can acclimatize him to this by holding or massaging his ear for a few seconds and then giving him a treat. I did this with my own cat. When I was learning to test I'd pop my cat up onto my desk, massage his ear, and give him a treat. Then I'd set up the testing kit, click the lancet device next to his ear, and give him a treat. Then, when I came to do a test 'for real' he was fine with that. And now he comes running when I rattle the test strip vial, and I can test him while he's dozing in his basket.
You and Zazu will find a way that works for you. Just be patient with yourself and you will be fine.
Eliz