Zorro used TA-Lib code.
TA-Lib a long time has not been updated.(last update 2007)
Is it reliable and safe to use?

No update in 10 years means that the product is already perfect.

Are the results(TA-Lib) similar to metatrader indicators?
for example MACD or RSI.

Are there any differences between TA-Lib and metatrader indicators?

They’re mostly the same.

If you question an indicator, you can always read the TA Lib source code, which is bundled with Zorro.

And since there are about 10 different versions of most MT indicators, there's a good chance that at least one of them matches the TA-Lib.

where is "includeta.h" in zorro directory?
version = 1.88

help file:
The TA-Lib function prototypes are defined in includeta.h.

The manual was wrong, they are in include\functions.h.