Two 8Ω tweets in series make them 16Ω. Now wire the two pairs in parallel for a final 8Ω load.
Or wire two pairs in parallel, then the pairs in series. 4 Ohm + 4 Ohm = 8 Ohms seen by amp.
This scheme allows you to still have the other 3 tweeters operating in case any one fails.
The other wiring scheme means you lose 2 tweeters if any one fails.