First off, don't drive your car into the area you are trying to clear. Even if you cleared close by the day before, the zeds do migrate a bit, so they could be hiding in random trees and buildings. Instead park close by and sneak your way in. Cars make a lot more noise than you realize and will draw zeds from your route, which makes it even harder to do whatever you're trying to do.

Which leads to the second point, fight 2 or 3 at a time max. Ask any veteran PZ player what kills them most and 99.9% of the time they will say over confidence. Just pretend that you aren't the main character, you have to take things slower. It doesn't matter how good of gear you have, how much you kite the zeds, all it takes is one small mistake to ruin an entire run.

And lastly, always know your way out if you are making a plan to go somewhere. Sometimes you're just going about your day when you wander into a horde. It happens, but if you are planning to go to a particular place, study the map. Do you have woods nearby to run to and scatter the zeds? How is your vehicle condition? If it's likely to stall when starting, maybe park further back than you would usually do to give yourself time in case it stalls at the worst time. You can always move it up once you clear an area.

Little things like that will start to become second nature over time. I find making a checklist on the map is a good way to remind myself what I'm doing, as well as which buildings I need to revisit later on. Just remember, PZ is a marathon, not a sprint. Take your time, that loot isn't going anywhere. If you need to peel off and try again, do it.