There have been a couple of very masculine trans women that I was friends with. Their sexual intentions were enough to end friendship. If there is no sexual attraction, their can only be friendship. Another problem is that women are expected to always be nice. Being nice can easily be misinterpreted as being interested.
For guys, trying to understand the difference between nice and interested can be confusing. Many like to assume she is hot for him. I tend to assume a guy is just being nice, until he commits sexual assault. Fortunately, that is rare, but it has occurred.
In the event a guy is interested in a woman, and thinks she is being flirtatious, it is best to politely ask. Then, accept her answer. If you have been friend-zoned, then decide if just a friendship is good enough. If not, go your own way, and look for someone else.