Zanni played his youth football with local club SC Buochs and after his time at school he started his apprenticeship as office clerk.
He was scouted by Grasshopper Club and in summer 1998 moved to their youth department, signing his first professional contract with them he interrupted his apprenticeship.
He went on to play 45 times for the GC, scoring one goal, until in November 2000 he suffered an injury and was kept out of the game until the end of the season.
He played well for one and a half seasons, until the end of 2004, and as Latour left the club Zanni also decided to leave.
[3] He played his domestic league debut for the club in the away game in the Espenmoos three days later, on 20 February, as Basel were defeated 3–1 by St.
[5] Basel completed all the 2004–05 Super League season's seventeen home games undefeated, winning thirteen and drawing four.
[7] Subsequently Basel dropped into the 2005–06 UEFA Cup, where against NK Široki Brijeg in the first round, they sealed a 6–0 aggregate win to qualify for the Group stage.
A last-minute goal from Zürich's Iulian Filipescu meant the final score was 1-2 in favour of the away team and it gave FCZ their first national championship since 1980–81.
[9] The next season Basel's European campaign started in the first qualifying stage of the 2006–07 UEFA Cup, here they beat Kazakhi side FC Tobol 3–1 on aggregate.
In the second qualifying round they were drawn against FC Vaduz from Liechtenstein, narrowly progressing on the away goals rule after a 2–2 aggregate draw.
At home against AS Nancy the match was drawn 2–2 and the final game ended with a 3–1 defeat against Wisła Kraków.
[11] Zanni was shown the yellow card 10 times this season, which meant that he missed two of the 36 league matches due to suspension.
Winning both matches in the qualification round and both matches in the play-off round, they team advanced to the group stage, which they ended undefeated in second position, after playing 1–0 at home against Stade Rennes, 0–0 away against Dinamo Zagreb, 1–0 at home against Brann and 1–1 away against Hamburger SV, to continue the knockout stage.
[16] In the Swiss Cup via FC Léchelles, SC Binningen, Grasshopper Club, Stade Nyonnais and in the semi-final Thun, Basel advanced to the final, and winning this 4–1 against AC Bellinzona they won the competition.
[18] Basel joined the 2008–09 UEFA Champions League in the second qualifying round and with an aggregate score of 5–3 they eliminated IFK Göteborg.
Here Basel were matched with Barcelona, Sporting CP and Shakhtar Donetsk but ended the group in last position winning just one point after a 1–1 draw in Camp Nou.
Carlitos took the corner kick and from the six-yard line Zanni headed the ball, out of the reach of goalkeeper Yann Sommer into the net.
[21] At the end of the 2008–09 Super League season Basel were third in the table, seven points behind new champions Zürich and one adrift of runners-up Young Boys.
After a goalless 90 minutes and extra time, YB decided the penalty shoot-out 3–2 and advanced to the final, only to become runners-up, as Sion became cup winners.
[23] For their 2009–10 season Basel hired Thorsten Fink as new head coach and Zanni found himself in a completely new situation.
Under coach Christian Gross Zanni had played four and a half years in virtually every game, but under Fink, he found himself on the bench.
On 7 February Zanni transferred free of charge to FC Vaduz in the Swiss Challenge League signing a two-and-a-half-year contract.