Given the good traffic you are receiving I suspect that you may soon receive an offer from a customer who will be trying to buy your home below the comp value. If you are flexible in your price it will sell. If you are steadfast it will sit.
My advice is be flexible and accept the fact that based on location your house is likely worth less than the homes used as comps. Also, ignore the Zestimate. No realtor worth their weight pays any attention to the way they evaluate homes.
Since your home is listed with an agent, the advice regarding marketing and any concerns should be discussed with your listing agent who was hired to sell your home, as per your listing agreement.
As a note ; Zillow and such third party sites that offer estimates, neither have accurate data nor are qualified to offer valuation for properties.
Would a mortgage lender make a loan based on a Zestimate ? Good question to ask a lender ;)
If it seems like they do not like the Highway, think about adding a privacy fence and some noise deadening trees. If its just the shape, not much you can do.
The market is very slow this time of year.
You are getting plenty of showings, so your marketing must be good.
Being below the Zestimate doesn't mean anything. Read Zillows information on their Zestimates and you will get a better understanding of how they get them.
If you are in comp range, have had all those showings with no offers, it means the buyers still think the house is overpriced. Once you find the number someone is willing to pay for the house, it will sell.
You can only control condition + price and availability to show it. Sounds like you are getting showings so you have some type of marketing working for you.
It may be a timing issue. Are there other similar homes selling in that time frame?