Well there are lots of ways you could learn programming in pawn.
1.
SA-MP Wikipedia.
Wiki wont make you a professional in pawn but it is required that you understand the things on it.It's also a good way to start off learning about pawn.
2.
Editing released gamemodes/fs
Most people learned a lot from editing gamemodes and filterscripts that were released on these forums.It's not easy though, you really need to put your effort and knowledge if you want to learn anything from looking at the code others wrote.You also can't expect to learn anything from editing if you don't have basic knowledge.
3.
Tutorials
These forums are full of tutorials on everything.Some are occasionally bad but some are really good.Other than these forums where are also a lot of tutorials that teach new comers pawn scripting on ******* as well.
4.
Learning by yourself
Many people (including myself) have learned most of the things they know by themselves.You will have a lot of problems at first, unsolvable errors but thats why the other three methods can also help and guide you threw them.
Here are some links that show you basics of ZCMD.But always remember, never jump to harder things, if you are not familiar with strcmp, I suggest you get started with that first.If you are, then checkout these following links.
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https://sampforum.blast.hk/showthread.php?tid=324389
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https://sampwiki.blast.hk/wiki/Zcmd
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https://www.youtube.com/watch?v=g5DUo42oF2g
You can feel free to checkout the many other tutorials posted here>>
http://forum.sa-mp.com/forumdisplay.php?f=70