Sounds like a trick question to me. Why?
Display: Just to display the 4-digit inputs - but especially the product, seems like you will need 8, 7-segment displays. If, for instance the problem was to multiply 9999 times 9999, you would need to display 99,980,001 (thats 8 digits). if you don't display the inputs, how do you know what you keyed-in and if you can't read the output, the project has no value. Setting up the 8 digits and driving them is complex by itself. Maybe the four digit numbers are "0101" and "0110"
I don't remember reading anything about power. You know, electricity. To make this thing work, you will need a transformer, bridge, regulator, and filter. Not too bad, but still requires parts that aren't listed by the teacher.
What about a keypad. You know, one of those little things with numbers on it, a "=" key, etc.
What the heck is a "control unit?" Perhaps it is one of those TI special function ICs made for calculating. Maybe we can use a $6 calculator as our "control unit."
Personally, I think there is a trick here and the teacher is on a power/self importance trip. PLEASE post the solution for us.