You should use HTTP GET/POST requests cubes and make requests with the parameters described in 2captcha API to solve this kind of captcha.
Check the example:
To run more threads, you should optimize your project.
First of all, disable unnecessary content loading on webpages, such as images, animation, media, etc..
If you work with large data, you should optimize the way processing it.
ZennoDroid works with apps, not browser as zennoposter. So cookies are not stored in a profile in ZD.
Try using this code to get cookies:
var cookie = droid.App.GetCookie("com.android.chrome");
return cookie;
There is nothing special here.
You should run instance with profile-folder and install browser extension, it will be saved in the profile.
Next time when you need the extension, just run instance with that profile-folder again
Please check my screenshot. There is a small button to stick the window and display it permanently or hide it.
Make panels reset and press this button.