'This parchment is plainly full of Dark Magic. This is supposed to be your area of expertise, Lupin. Where do you imagine Potter got such a thing?' said Snape. Lupin looked up and, by the merest half-glance in Harry's direction, warned him not to interrupt. 'Full of Dark Magic?' he repeated mildly. 'Do you really think so, Severus? It looks to me as though it is merely a piece of parch- ment that insults anybody who tries to read it. Childish, but surely not dangerous? I imagine Harry got it from a joke-shop -' 'Indeed?' said Snape. His jaw had gone rigid with anger. 'You think a joke-shop could supply him with such a thing? You don't think it more likely that he got it directly from the manufacturers?’ Harry didn't understand what Snape was talking about. Nor, apparently, did Lupin. 'You mean, from Mr Wormtail or one of these people?' he said. 'Harry, do you know any of these men?' 'No' said Harry quickly. 'You see Severus?' said Lupin, turning back to Snape. 'It looks like a Zonko product to me -' Does this mean Snape knew James, Sirius, Lupin and Peter's nicknames were Prongs, Padfoot, Moony and Wormtail respectively? If he did, why did Lupin continue with the Zonko theory even though he knew it was no use? Isnt this like - ' A person sees you drawing a painting. After completing it, you show it to him and tell him a best friend of yours drew it. ' Isnt it just pointless?

Snape did know about that stuff, but harry said he didn't. Although he did, snape did not know. Lupin did not want to let snape know he knew because of the map they made... (i think)

Yes, Snape did know who they were.

yes he did remember he was constantly taunted by the marauders in his school days.

Snape did know exactly whose parchment that was. Did you notice that "directly from the manufacturers" was italicized? He was accusing Lupin in a few careful words. Lupin, likewise, had to speak carefully. Mind you, he still thinks that Sirius is a murderer out to get Harry, and Sirius had a hand in making the map. If you read on, I believe that Lupin suggests that the creator is trying to lure Harry out of safety. Lupin's just being very cautious about revealing his part in the map-making, for whatever reasons. Perhaps he thinks Harry will trust the map knowing that Lupin helped make it only to be trapped by Black. Maybe he didn't want Harry to know that he was friends with Sirius who (seemingly) turned out to be Voldemort's greatest supporter. At this point, Lupin's motives aren't clear, but he isn't trying to fool Snape, but trying to protect Harry.