For example , if I want whether player enter the trigger zone , an entity spawn / or be destroyed / a zombie come to attack player / open a gate . Is it possible to make it easily?

Firstly, welcome to the Forums as I see you have joined today. Yes it is possible. Check out the twitch broadcasts TGC have done on YouTube or read the forums, this question has been asked many times, feel free to search the forums and also check out the TGC GG video tutorials(links are also within GG menu).
You can achieve this by LUA scripting or using the "ifused" parameter in the trigger zone to trigger an entity that you want to spawn etc, but I recommend reading/watching tutorials, there is a wealth of knowledge on the forums and some very clever/talented people who can answer any question you have.

This may help you ....