Article 5 of (EU) 261/2004 states in its 1.
In case of cancellation of a flight, the passengers concerned shall:
(a) be offered assistance by the operating air carrier in accordance with Article 8; and
(b) be offered assistance by the operating air carrier in accordance with Article 9(1)(a) and 9(2), as well as, in event of re-routing when the reasonably expected time of departure of the new flight is at least the day after the departure as it was planned for the cancelled flight, the assistance specified in Article 9(1)(b) and 9(1)(c); and
(c) have the right to compensation by the operating air carrier in accordance with Article 7, unless:
(i) they are informed of the cancellation at least two weeks before the scheduled time of departure; or
(ii) they are informed of the cancellation between two weeks and seven days before the scheduled time of departure and are offered re-routing, allowing them to depart no more than two hours before the scheduled time of departure and to reach their final destination less than four hours after the scheduled time of arrival; or
(iii) they are informed of the cancellation less than seven days before the scheduled time of departure and are offered re-routing, allowing them to depart no more than one hour before the scheduled time of departure and to reach their final destination less than two hours after the scheduled time of arrival.
And article 8 states:
Where reference is made to this Article, passengers shall be offered the choice between:
(a) - reimbursement within seven days, by the means provided for in Article 7(3), of the full cost of the ticket at the price at which it was bought, for the part or parts of the journey not made, and for the part or parts already made if the flight is no longer serving any purpose in relation to the passenger's original travel plan, together with, when relevant,
- a return flight to the first point of departure, at the earliest opportunity;
(b) re-routing, under comparable transport conditions, to their final destination at the earliest opportunity; or
(c) re-routing, under comparable transport conditions, to their final destination at a later date at the passenger's convenience, subject to availability of seats.
As far as I understand, OP has been offered a re-rerouting as foreseen by the (a) of Article 5.1. He had then choosen for option (c) of Article 8.1 (re-routing at passenger's convenience).
Separately, and no matter of its decision regarding the choice offered by Article 8, OP may be eligible to a compensation if the Swiss flight has departed more than 1 hour before its original scheduled departure time (which should be the case if he has been offered a seat on LX87).