not necessarily practical. Both firewalls will be listening for the same traffic on the same ports.
Some people experience software conflicts when trying to run two firewalls while others have no issues. Much depends on the underlying hardware of your system, its software setup and its connection to the web.
I'd stick with one or the other.
A bi-directional firewall is theoretically more effective since it tracks inbound and outbound traffic requests but some of the bi-directional firewalls are less effective than they could be which is where a product review can help to highlight a more effective product.
The short answer is yes you can. I see no real benefit though.