Is that feasible for me to conduct a study of the effects of a teaching intervention on students' receptive skills, meaning reading and listening skills simultaneously? Is that too many things that I should focus on to implement?
It would be more clear if you will conduct a study one by one (e.g., reading & listening) since we are to determine the intervention in a receptive skill of a learner that you may find out its effect, after another one, this may give you a clear bunch of data and affects provided the intervention. You may also weight the average using your statistics and interpret data accordingly.
On the case of simultaneously, you can also do it however the data is affected provided or as against to my first suggestion they have enough time, however for simultaneously, time affects the data which is one of the constraints of the result.
You may measure both receptive skills (reading / listening) of the students in the same teaching project, but with different instruments. The question whether it does make sense, depends on the kind of teaching intervention, as you will know.