On a serious note: I see the difference between a voyage of discovery - i.e. South America and a voyage of trade i.e. tribute.
If we still acknowledge that the Chinese at the time had visited the Med, knowiong about Venice, Genoa, etc etc. we should see some records (outside of Menzie, OK).
Now, if we reject Menzie, do we thereby also say the Chinese did not kow about Europe and West Africa?
If we reject Marco Polo, do we thereby say the Europeans did not know about China? Of course not. Now, very likely most Chinese didn't know a thing about Europe, but all anyolne with an interest in these matters had to do was ask an expert. From China's POV, the experts on Europe were the Persians, Arabs and Turks. With a ready source of knowledge at hand, why would they need to go exploring themselves? And if they did - which is really not at all unlikely - why would that do so in ships? The idea that explorers come in big boats is a European conceit. If the Chinese court had a genuine interest in getting a first-hand description of Europe, the natural thing to do would be to put some scholars and artists on a regular passenger ship to Calicut or Mecca. From there, they could take passage to Syria or Egypt, and then book a trip across the Mediterranean. Alternatively, you could put them on horses and send them off along the Silk Road till they reached Ottoman territory. From then on, it's all civilised lands until you hit Hungary.
Not visiting Western Europe is like saying "I want to go to Jupiter's moon, because it is empty, not to Mars. I know there are civilisations on Mars, but i feel like skipping that part". Not even NASA could justify it.
Oh dear. Western Europe was not the civilised countrerpart at the end of a howling wilderness that the Chinese vainly struggled to contact. It was a moderately interesting, but largely familiar variation on the theme of "civilisations of the far west". The Chinese had information, but really no pressing need to go. Any voyage to Europe would not have been a voyage of explopration, but simply one of going-somewhere-you've-heard-of-but-don't-particularly-care-about.
Seriously, this is a bit like asking what band people in Central Africa were fans of in the 1960s, since it wasn't the Beatles. The answer is, no band. Going off in ships at random to smash up natives, grab loot and draw maps was a European thing. The Chinese were into power projection, but not like that.
So, were they voyages of discovery or tribute?
On the first point, not likely, since the Chinese had no need to dioscover Europe. They knew where it was and what it had to offer. On the second point, no, because the Chinese had no way of extracting tribute from Europe.