Legal Question in Business Law in California

The right to partition property can be waived. This language is pretty awkward, but it sure sounds like the parties to this agreement will have waived their right to partition under the statutes and substituted whatever property-division provisions are in the agreement itself. Without seeing the entire agreement, I could not be 100% sure the provision is legal, but there is nothing illegal per se about a waiver of the right to partition. That happens fairly frequently and for a variety of reasons, including but not limited to express waiver in terms such as "The parties hereto hereby expressly waive their right to partition the property."

A contract cannot require an illegal act, but it can waive the parties' legal rights. That's what this contract is at least trying to do. Offhand I can't say whether it did so properly or whether the language you quote would be enforceable.