Answer:
Here is the Python code to create a vehicle class with a constructor that initializes maxspeed and mileage to 0:
```
class Vehicle:
def __init__(self):
self.maxspeed = 0
self.mileage = 0
```
This constructor function takes no arguments, but initializes the data attributes `maxspeed` and `mileage` to 0.
You can then create an instance of this Vehicle class simply by calling the class constructor, like this:
```
mycar = Vehicle()
```
Now the `mycar` object has `maxspeed` and `mileage` set to 0, and you can modify these attributes as needed.