Guess I don't understand what you are getting at. Both the email addresses are different, and the IP addresses are different and you are asking if it's possible that one computer or one person sent both emails.
It's the ISP that determines the IP address, not the computer. Computers are connected to the internet either through a wifi server, or a modem. It's the server or the modem that gets assigned the IP address. In a home or business network situation computers have individual IP addresses, that allows multiple computers to use one network ISP through a hub or router. The IP address you see on an email is the IP address of the ISP servicing that account. The ISP can give you the physical address location of the computer that sent the email, but you would need a court order to see that information.
If the person had a laptop, he could send one email from one location, say his home, then go to his buddies house, hook into his internet service and log into a different email account and send the email again. In this case, both the email and IP addresses would be different.
He could send one email from home, go to his buddies house, and use his buddies computer, log into a different email account and send the email again. In this case, both email and IP addresses would be different