Connect two webforms?
I am not sure about your control here, whether to move from survey webform to task webform or the vice versa. But this is what I would do.,


On login query the "webform_submissions" table with the logged in user's id and see whether he/she has submitted the webform before.
If he/she has not submitted it before load the webform say task webform.
If he has submitted this before, load the survey webform page.


You can make use of "hook_user_login" to redirect on login, also this can be used to query the "webform_submissions" table.