I beleive it was the 92-93 season,the final one in fact.

Zack was helping Lisa with a fashion show,he was in her room and was leaving and out of nowhere they kissed.The next day,they talked about the kiss at the MAX,and ended up kissing again.The same day,they were holding hands and telling each other how much they liked the kiss.The show ended,with Zack and Lisa walking off holding hands,set to date or maybe even start a relationship.

The funny thing is,it just vanished the following week.

I guess the writers wanted to give Zack one day each in the series run to explore love with Jessie/Lisa.The only difference is Zack/Jessie decided to remain friends,while Zack/Lisa appeared to be couple bound.

ya i noticed that too. it was weierd. i wanted to see them be a couple

Thats happened way too many times.

- Jesse's stepbrother, whom they asked to stay at Bayside.
- Slater dating Denise Richards at the Malibu Sands Beach Club, then syaing she was going to Bayside
- Zack dating the fat girl from the date auction
- Zack dating the wheelchair girl

The list goes on and on..

dont forget about the movie as well where zack fell in love with andrea and couldnt live without her