Predict part of the input for a fixed target
I am not sure what is the scale of your dataset, but I guess what you're looking for conceptually is Multi-task learning. You can use this concept to carry out multiple tasks, or in your case regression predictions using a single model.What you can try doing is use the four features, and the target variable as input features to predict the two variables. 

If you have a large dataset, you can look into deep learning multi-taking approaches here. If you are familiar with python and sklearn, you can try some basic multi task regression algorithms available as a starting point. This algorithm might be helpful, its easy to use. If you are looking for a more deep learning approach, there are many architectures available online that you can try as starting point.